MffiY LAB0SAT08Y 
EXEBCISES 



ON MILK COMPOSITION 

AN® TESTfS 



H. C. TROY 

T. J, McINERN£Y 




CopightN . 



COPYRIGHT DEPOSTT. 



DAIRY LABORATORY EXERCISES 



ON 



TESTING AND COMPOSITION OF DAIRY PRODUCTS 



BY 



H. C. TROY and T. J. MdNERNEY 

Profeasor of Dairy Industry in Charge Assistant Professor of Dairy Industry, 

of Testing and Composition of Dairy City Milk Inspector. 

Products, Consulting Chemist of 
New York State Department 
of Farms and Markets. 



New York State College of Agriculture at Cornell University 



FIRST EDITION 



ITHACA, NEW YORK 

Ithaca Publishing Company 

117 South Tioga Street 

1921 

ALL RIGHTS RESERVED 



II 



-1*1 



Copyright 1921 

By 

H. C. TROY and T. J. McINERNEY 



BCI.A627273 



OCI -6 Ml 



TABLE OF CONTENTS 

PAGE 

I. The General Composition of Milk 1 

II. The Babcock Fat Test 5 

III. Testing Butter for Moisture 37 

IV. The Specific Gravity of Milk and the Use of Lactometers 41 

Y. The Acidity of Milk 55 

VI. Cheese Moisture Test 62 

VII. Salt in Butter and Butter Salt Test 67 

VII. Cow Testing Association Records 75 

VIII. The Majonnier Test for Fat and Solids in Milk and Its Products-- 102 

PART I EXEBCISES 21 

I. The Babcock Test 22 

II. Conformity of Babcock Glassware to Specifications 25 

III. Accuracy of Calibrations and Speed of Centrifuge 28 

IV. Testing Skim-Milk and Cream 31 

V. Modifying Tests 34 

VI. Babcock Test, Butter Moisture Test 38 

VII. Effect of Temperature and Different Amounts of Acid and Use of 

Quevenne Lactometer 45 

VIII. Composition of Milk and Test for Boiled Milk 49 

IX. Babcock Test and Calculating Adulterations 52 

X. Babcock Test, Acid Test and Density 58 

XL Cheese Moisture Test, Babcock Test, Acid Test and Lactometer 64 

XII. Babcock Test, Use of Hand Machines, Acid Test, Butter Moisture 

and Salt Tests 69 

XIII. Microscopical Appearance of Milk, Use of Rennet, Salt Test, Bab- 

cock Test 72 

XIV. Babcock Test, Cow Testing Association Experiments 76 

XV. Testing Sour Milk, Effect of Temperature, Use of Different Aeids__ 80 

PABT II EXEBCISES 83 

XVI. Variations in Composition of Milk, Acid Test, Adulteration 84 

XVII. Comparing Different Fat Tests, Effect of Temperature and Test- 

ing Milk Powder 88 

XVIII. The Babcock and Shaw Butter Fat Tests 91 

XIX. Comparison of the Babcock and Adams Tests for Fat in Milk 95 

XX. Composition of Butter by the Gravimetric and Kohlman Method^-- 99 
XXI— XXII. The Majonnier Tests for Milk Fat and Solids 103 



VI 

PAGE 

XXIII — XXIV. Testing and Standardizing Before Condensing a batch 

for the Manufacture of Evaporated Milk 106 

XXV — XXVI. Testing and Standardizing Before Condensing a Batch 

for the Manufacture of Sweetened Condensed Milk 109 

XXVII— XXVIII. Testing and Standardizing lee Cream Mix 112 

XXIX — XXX. Testing and Standardizing Ice Cream Mix (Con- 
tinued) 115 

XXXI — XXXII. Testing and Standardizing Ice Cream Mix (Continued) 118 

XXXIII— XXXIV. Making and Cheeking Standard Acid and Alka- 
li Solution 121 

XXXV— XXXVI. Milk Analysis and Modified Leffman-Beam Method for 

Pat in Milk and Cream 125 

XXXVI. Hart and Walker Casein Tests, Gerber Fat Test 129 

XXXVIII. Determining the Solubility, of Casein 132 

XXXIX. Detecting Butter Substitutes 136 

XL — XLI. Reiehert-Meissl Number of Butter and Oleomargarine, Mak- 
ing Viscogen 139 

XLII— XLIII. Modifying Milk for Infants and Invalids 143 

XL.IV — XLV. Testing Unsweetened Evaporated, Sweetened Condensed 

Milk and Ice Cream 147 

XL VI— XLVII. Test for Preservatives, Adulterants and Boiled Milk— 154 

List of Bulletins 160 

Index 164 



Ill 



PREFATORY NOTE 

This book is intended to provide an outline of 
exercises for students in dairy industry. It is not 
intended that it should serve as a text book. 

The exercises in Part I may be used in all schools 
and colleges as an introductory course on the testing 
and composition of dairy products. 

The exercises in Part II are intended to serve as 
an advanced course for those specializing in dairy 
work and food control work. 

Ithaca, X. Y., October 1st, 1921. 



IV 



Dairy Laboratory Exercises 



GENERAL COMPOSITION OF MILK 

The fluid normally secreted in the mammary gland of female 
mammalia is called milk. In defining the standards of purity 
for dairy products the Association of American Dairy, Food and 
Drug Officials adopted the following definition of milk on August 
3rd, 1917:— 

"Milk is the whole, fresh, clean lacteal secretion obtained by 
the complete milking of one or more healthy cows, properly fed 
and kept, excluding that obtained within fifteen days before 
and five days after calving, or such longer period as may be 
necessary to render the milk practically colostrum-free." 

The six main constituents of milk and their approximate 
percentage is shown in the following chart: — 



Total 
Solids 



"Water 

Fat 

Sugar 
Proteins ( Casein 
3.45% (Albumin 

Ash or mineral matter 



87.42% 
3.80% 

f 5 J )solids 

2 - 75 % (not 

■ m °/° (fat 
.70%) ±at 



Tofa/ 
so//(fs 






08. -*3o£ 



3* 



r<7t3cf a 



Xlbcmlp .ZrZg- 



Wafer Be.-+3cf 



Tofa/ 
so//c/s 



Wafer 
65.4-7% 




E/verqi/ un/fs 580 Energy un/fs 800 

Corr7p?or(7//re -footf fa/ue. Corr?pcrraf/re -food ^a/ue 

/Octs. f?er qf, /*cfs. per erf 

FIG. 57. COMPARISON OF AVERAGE COMPOSITION AND POOD VALUE OF MILK CON- 
TAINING THREE AND FIVE PER CENT OF FAT 



2 COMPOSITION OF MILK 

The difference in the food values of equal quantities of milk 
containing different percentages of fat is shown in figure 57. A 
1-per-cent increase in the percentage of fat in normal milk indi- 
cates about a 20-per-cent increase in the food value. Thus when 
a quart of milk containing 3 per cent of fat is worth 10 cents, a 
quart containing 4 per cent is worth 12 cents, and a quart con- 
taining 5 per cent is worth 14 cents. These facts have not been 
generally understood in the past, and have not received sufficient 
attention in the retail marketing of milk. They point out the 
importance of the fat test. 

One hundred pounds of milk containing 3 per cent of fat will 
make about 3.6 pounds of butter, while the same weight of milk 




A 



B 



(' 



Fig. 58. AMOUNT OF butter made from one hundred pounds of milk con- 
taining VARIOUS PERCENTAGES OF FAT 
A, one hundred pounds of milk containing 3 per cent of fat made 3.6 pounds 
of butter; B, one hundred pounds of milk containing 4 per cent of fat made 
4.8 pounds of butter; 'C, one hundred pounds of milk containing 5 per cent 
of fat made 6.0 pounds of butter 

containing 5 per cent of fat will make 6 pounds of butter (fig. 58.) 
This shov s the importance of testing milk when calculating its 
butter-]' aking value. The increase in the number of pounds of 
butter over the number of pounds of fat in the milk or the cream 



COMPOSITION OF MILK 3 

is called the overrun and it is due to the water, the salt, and the 
casein that remain in the butter when the churning process is 
completed. One hundred pounds of butter of average compo- 
sition contains about 82 pounds of fat, 14.5 pounds of water, 
2.5 pounds of salt, and 1 pound of casein. 

The percentage of fat in milk also indicates its cheese-making 
value. Thus while 100 pounds of milk containing 3 per cent of 
fat will make on an average about 8.3 pounds of cheese, the same 
amount of 4-per-cent milk will make 10.6 pounds, and a like 
amount of 5-per-cent-milk will make 12.9 pounds. 

Fat exists in milk in the form of very small globules. With the 
aid of a high-power microscope t\iey may be seen floating in 
the liquid. Since the fat globules are lighter than the other milk 
constituents, most of them rise to the surface under the influence 
of the force of gravity. There, mixed with other milk substance, 
these globules form a layer of cream. 

When sulfuric acid of proper strength and temperature is 
added to milk, as in the Babcock fat test, the milk sugar, and 
the protein are decomposed, and the sticky quality of the milk 
is destroyed. The acid does not, however, decompose the fat, 
"but leaves it free to come to the surface of the mixture under 
the influence of centrifugal force generated in the testing 
machine. 

FAT VARIATIONS IN MILK 

The fat in milk commonly varies between three and six per 
cent. These variations come from several causes. One of the 
most important is the breed of the cows ; another is the difference 
between individuals of the same breed. The percentage of fat 
in the milk of an individual in extreme cases may average either 
one per cent above or one per cent below the breed average. 
Also, the percentage of fat is affected by the length of time since 
the cow has freshened. It is a well-known fact that toward the 
end of the lactation period, Avhen the cow is being dried off, the 
milk contains a higher percentage of fat than it did earlier in 
the season. It is also fairly well established that, when the time 
elapsing between milkings is not of equal length, the milk drawn 
after the longer period contains the lower percentage of fat. 
There are also minor influences affecting the fat content, such as 
feverish condition of the animal, or overexcitement due to dog- 



4 COMPOSITION OF MILK 

ging or other ill treatment that might cause the cow to hold up 
part of her milk, thus giving a larger portion of the milk that is 
first let down, which is not so rich in fats as the strippings. The 
character of the food of an animal has very little effect on the 
percentage of fat in the milk, altho it has a marked effect on the 
amount of milk and fat produced. 

FAT PERCENTAGE AND FOOD VALUE 

When measured by energy units, the fat supplies about one- 
half of the food value of average milk, and the solids not fat 
furnish the other half. The solids not fat are composed of milk 
sugar (lactose), casein, albumin, and mineral matter (ash). 

Recently it has been discovered that milk also contains two 
very important growth-promoting and health-regulating prin- 
ciples, known as vitamines. 

The principal proteins in fresh milk are calcium casemate, 
lactalbumin and lacto-globulin. The casein is not in true solution 
but is evenly distributed throughout the mass of milk in minute 
gelatinous particles known as a colloidal condition. The casein 
assists in retarding the rise of fat globules and is largely account- 
able for the opaque, nearly white color of milk. In fresh milk 
it is not precipitated by boiling but is thrown down by dilute 
acids while strong mineral acids dissolve and decompose it. Milk 
albumin is present in true solution. It is not precipitated by 
dilute acids but is thrown down by heating milk to a temperature 
of about 80° C. Lacto-globulin is present in milk only in traces. 

Milk sugar forms about 58 to 60 per cent of the solids not fat. 
It is valuable chiefly as a food, having the same energy and heat 
producing power as cane sugar but it is not so sweet. It is con- 
verted to lactic acid by bacterial action and its presence in the 
digestive tract is thought to assist digestion. The importance 
of milk sugar is also increased since lactic acid and its control 
plays an important part in the manufacture, quality and preser- 
vation of milk products. 

The ash is the substance derived from the mineral salts of 
milk that remain when dried milk is burned to a white ash at a 
low red heat. The mineral salts in milk consist chiefly of potas- 
sium, sodium, calcium and magnesium in the form of chlorides, 
phosphates and citrates. The high calcium content gives the 
mineral salts of milk special value as a food. 



THE BABCOCK FAT TEST 5 

THE BABCOCK FAT TEST 

Previous to the year 1890 comparatively few people knew any- 
thing about the composition of milk or the percentage of fat it 
contained. Dairy products were bought and sold by weight 
or measure almost regardless of their composition or food value. 
In 1890 Dr. S. M. Babeock of the Wisconsin Agricultural Experi- 
ment Station invented the milk fat test that bears his name and 
published a report on it. By the application of this test, or 
slight modifications of it, the approximate percentage of fat in 
nearly all dairy products many be determined. 

TESTING MILK 

Sampling the Milk. If the milk is fresh and no cream has 
risen on it, the sample shall be taken immediately after pouring 
the milk from one vessel to another three or four times. Where 
such milk cannot be poured, it should be thoroughly and vig- 
orously stirred for at least half a minute with some suitable 
instrument long enough to 'reach the bottom of the container. 

If the cream has risen on the milk, or if a layer of cream has 
formed, mixing must be continued until all cream is detached 
from the vessel and all particles of cream are broken up and 
evenly distributed throughout the mass and no longer are visible 
on close observation. 

In taking composite samples, a porportionate amount of each 
mass of milk sampled should be placed in the composite sample 
bottle. This can usually be done best by means of a sampling- 
tube. At least ten cubic centimeters of milk should be taken 
from each mass of milk sampled. A composite sample, as referred 
to here, means a sample of milk made up of proportionate 
amounts of each delivery from a single source, to be tested for 
fat content. A composite sample should not represent milk de- 
livered for a period of more than 16 days. A herd sample taken 
one day during the period cannot be considered a composite 
sample of such period. 

Care of the Milk Sample. Composite samples in order to 
give satisfactory results, should be kept in a shaded place in 
clean, air-tight jars and should contain a sufficient amount of 
preservative. Corrosive sublimate or potassium bichromate shall 
be used as preservatives, care being taken not to use excessive 



THE BABCOCE FAT TEST 



amounts. Care also should be taken to keep such samples in a 
cool place, but they should not be allowed to freeze. 

If transported by mail, express or otherwise, the sample bottle 
should be completely filled, tightly stopped and sealed. 

Immediately before testing, the sample must be mixed gently 
until it is homogeneous. Composite or other than fresh samples 
must be placed in water warm enough to soften all lumps of 
cream and cream attached to the inside of the jar. Then mix 
gently until the sample is homogeneous and pipette at once, 
using 18 grams of milk. Avoid incorporating air bubbles while 
mixing the sample. Curdy and churned samples are not de- 
pendable. 

Operation: Mix the 
milk by pouring, allow- 
ing it to flow down the 
side of the vessels to 
avoid incorporating air 
bubbles. Vigorous shak- 
ing should be avoided. 
See that all cream is 
removed from the sides 
of the sample bottle and 
that it is evenly distrib- 
uted thruout the milk. 
Then holding the pi- 
pette between the 
thumb and the second 
finger of the right 
hand, place its tip well 
under the surface and 
draw in the milk by 
suction with the lips on 
the upper end until it 
is filled well above the 
graduation. Quickly 
place the fleshy pad of 
the forefinger over the 
opening and at right angles to the pipette. By rolling the pipette 
a little between the thumb and the second finger sufficient air will 
enter to allow the milk to run out slowly until the upper surface 




Fig. 61. correct position of the pipette 
and test bottle while transferring the 

MILK 



TEE BABCOCK FAT TEST 



is exactly level with the graduation. The pipette should be held 
perpendicular, with the graduation on a level with the eye. 

Hold the milk test bottle in a slanting position and place the 
tip of the pipette into it about one-third of an inch and at a slight 
angle (fig. 61). Allow the milk to flow slowly down the side of 
the bottle neck, making certain that none is blown out by the 
escaping air. Blow the drop that remains at the tip of the 
pipette into the test bottle. Measure out another test sample in 
the same manner, as the test must be made in duplicate. 

Adding' the Acid: Fill the measure to the mark with acid, 

and then rotate the test bottle 
slowly while adding the acid so 
that it will rinse down any milk 
remaining in the neck. Imme- 
diately mix the acid and the milk 
thoroly by whirling the body of 
the bottle in a circle five or six 
inches in diameter (fig. 62), using 
care to keep the mixture out of 
the neck of the bottle. Shake 
the mixture vigorously for about 
one minute after all curd has 
disappeared, and shake it again 
just before centrifuging to in- 
sure complete solution. Avoid 
pointing the neck of the bottle 
toward any person during the 
mixing operation and so prevent the possibility of having acid 
thrown into the eyes or on the clothing. The acid unites with all 
of the milk substances except the fat, thus generating much heat. 
The temperature of the mixture usually rises to 225° F. 

Centrifuging: Steam driven centrifuges will be warm enough. 
Hand or electrically driven centrifuges are heated either by 
placing on a stove or by adding a few quarts of boiling water. 
A corked opening in the bottom provides a means of removing 
the water. 

The disk of the machine must be balanced by placing test 
bottles in exactly opposite pockets. Cover the machines before 
starting. 




Fig. 62. diagram showing the mo- 
tion AND POSITION OF A TEST BOT- 
TLE WHILE MIXING THE MILK AND 
THE ACID 



8 THE BABCOCK FAT TEST 

Table showing the revolutions per minute the bottles should 
make while whirling in Babcock testers: 

10 inch disks 1,100 revolutions 

12 inch disks 1,000 revolutions 

14 inch disks 925 revolutions 

16 inch disks 850 revolutions 

18 inch disks 800 revolutions 

20 inch disks 760 revolutions 

22 inch disks 725 revolutions 

24 inch disks 700 revolutions 

The diameter of the disks may be determined by measuring 

the distance between the bases of bottles in opposite cups when 
they are in a horizomtal position. 

After whirling the bottles for five minutes, stop, and, without 

removing the bottles from the pockets, fill them nearly to the 

base of the neck with water that is nearly boiling hot. The 

pipette or a tin cup with a slender spout may be used for this 




Fig. 63. pouring the hot water into the bottles 



purpose (fig. 63). Whirl the bottles again for two minutes in 
order to wash any sediment from the fat. Again add hot water 
to the test bottles until the top of the fat column is a little 



THE BAB COCK FAT TEST 9 

below the highest graduations on the scale. Whirl the bottles 
for one minute, and take the readings immediately. If the tests 
are not read immediately, they should be held at a temperature 
between 130° and 140° F. either by keeping the centrifuge hot 
and covered or by placing the test bottles in water at that tem- 
perature and deep enough to surround the fat columns. 

Reading- the Percentage of Fat: Subtract the reading on the 
scale at the base of the fat column from the reading at the high- 
est point at\the top of the fat column (fig. 64.) The difference is 
the percentage of fat in the milk. Thus, if the scale at the base 
of the column reads 1.7 and at the top reads 5.8, then 5.8 minus 1.7 
equals 4.1, the percentage of fat in the milk. The curved surface 
called the meniscus, which always exists at the top of the fat 
column, must be included in the reading, as it is just large enough 
to make up for a small amount of fat remaining down in the body 
of the bottle. The limit of error for the test is usually less than 
.2 of 1 per cent. When such a difference occurs in a duplicate 
test, the average of the duplicate readings should be taken. 



TESTING CREAM 

Sampling": Cream differs from milk by containing a higher 
percentage of fat. Cream containing 30 per cent of fat would 
contain 70 per cent of skimmed milk substance, or milk serum. 
Before sampling, the fat should be evenly distributed by thoro 
mixing or pouring. If the cream is old or lumpy or some has 
dried on the container, it should be warmed to about 95° F. and 
the lumps should be passed thru a strainer before mixing. Then 
about two ounces should be placed in the sample bottle. 

Operation: The test sample must 'be weighed instead of meas- 
ured because : 

1. The percentage of fat and the specific gravity of cream vary 
widely, and the weight of a definite volume would vary ac- 
cordingly. 

2. Cream may contain bubbles of air or of carbon dioxide. 

3. Cream varies so widely in viscosity (sticky quality) that 



10 



TEE BABCOCK FAT TEST 




the amount delivered or the amount remaining in the pipette 
would be unknown. 

In testing cream 9 grams is used. Balance the bottle on the 
scales, and place a 9-gram weight on the oppo- 
< v ,) site side. Mix the sample thoroly, and by means 

of a pipette transfer cream to the test bottle 
until the scales exactly balance. Next add 
about 9 cubic centimeters of water to the test 
bottle. This water may be measured with suf- 
ficient accuracy in the acid measure by filling 
it a little over halfway to the mark. Add about 
15 cubic centimeters of the acid to the test 
bottle, and mix the contents thoroly. The 
cream and acid mixture should not turn black, 
but should remain coffee color. About 15 cubic 
centimeters of acid gives the proper concen- 
tration to dissolve the solids not fat, since the 
fat forms such a large part of the mixture and 
does not go into solution. Centrifuge the bot- 
tles, and add the water exactly as in testing 
whole milk. 

Tempering the Fat and Reading the Per- 
centage : When the last whirling is completed, 
transfer the test bottles to the tempering vat 
containing water held at a temperature of 
140° F. The water should be tempered in ad- 
vance, and it should be deep enough to sur- 
round the necks of the bottles to the top of 
the fat columns. After four minutes take the 
bottles from the water, and add the meniscus 
remover at once by placing the tip of a drop- 
ping pipette containing some of the substance 
against the inside of the neck of the bottle, 
which is held in a slightly slanting position. The red liquid is 
allowed to run slowly down the inside of the neck and spread 
over the fat to a depth of about one-fourth of an inch. It should 
not mix with the fat. Read the test immediately by subtracting 
the number on the scale at the bottom of the fat column from 
the number on the scale at the line of division between the fat 
and the meniscus remover (fig. 65). Thus if the bottom line of 



Fig. 64. method 
of reading the 
percentage of 
fat in milk 
The arrows in- 
dicate the points on 
the scale at the 
ends of the fat col- 
umn at which the 
readings should be 
taken 



THE BABCOCK FAT TEST 



fle/7/scus 
remoter 



Wk" 39 <& 



the fat column reads 12 and the line between the meniscus re- 
mover and the fat at the top reads 39, the percentage of fat 
would be 27. 

In testing milk the meniscus should be included in the reading 
as it is just sufficient to make up for the fat that is not brought 
up by the test. But the volume of the meniscus on the cream test 
is much larger than the one on the milk test, while the amount, 
of impurities in the larger volume of fat in the cream test is about 
sufficient to make up for any fat remaining down in the bottle. 
Therefore, the meniscus on the cream 
test should be removed before reading* 
the percentage of fat. 

APPEARANCE OF A COMPLETED 
TEST 

In a completed test the fat should 
be straw-yellow in color; the ends of 
the fat column should be clearly and 
sharply defined; the fat should be free 
from specks and sediment ; the water 
in the neck just below the fat should be 
clear; and the fat should be in the 
graduated part of the neck. Some of 
the defects and remedies are explained 
in the following paragraphs. 

If the fat column is too dark in color, 
the acid may have been too strong, or 
too much may have been used, or the 
temperature of the milk and the acid 
may have been too high just before 
mixing. Mixing too slowly might also 
permit charring of part of the fat. The 
charred or darkened condition of the 
fat may be corrected to some extent by 
using less acid, by cooling both milk 
and acid below 60° F. just before mix- 
ing, and by rapid vigorous mixing con- 
tinued for about a minute after all 
casein has been dissolved. 

If the fat column is too lijht in color, 
the acid was either too weak or too 




Pig. 65. method of read- 
ing THE PERCENTAGE OF 
FAT IN CREAM 

The arrows indicate the 
points on the scale at the 
ends of the fat column at 
which the readings should 
be taken 



THE BABCOCK FAT TEST 



cold. This condition may be corrected to some extent in succeed- 
ing tests by using more acid and by having the milk and the acid 
at a little higher temperature when brought together. 

If the acid is not of the correct strength (specific gravity 1.82 
to 1.83), it will be difficult to get a correct test, but the trouble 
may be partially overcome by using more acid when it is weak 
and less when it is too strong. 

TESTING SKIMMED MILK AND BUTTERMILK 
The skimmed milk test bottle (fig. 66) is also used in testing 
buttermilk, and the operation is the same for each substance. 
The graduated neck of the skimmed milk test bottle has a very 
small bore in order to measure the fat accurately. A second 
neck with larger bore is attached to provide a convenient means 
of filling the bottle. The smallest di- 
visions on the scale usually indicate 
.01 of 1 per cent, but on some bottles 
they indicate .05 of 1 per cent. 

The same care is necessary in mixing 
and sampling skimmed milk and but- 
termilk that is required for whole milk, 
and the same pipette is used in measur- 
ing out the sample. The skimmed milk 
is added to the test bottle thru the 
larger neck. Since a little more acid 
is necessary to thoroly free the fat in 
skimmed milk, 23 to 25 cc. should be 
used. First add about one-half of the 
acid, and shake the mixture thoroly; 
then add the remainder, and again 
shake it vigorously for about a minute. 
Avoid throwing undissolved casein in- 
to the small neck while mixing the milk 
with the acid. The bottles are then 
centrifuged and filled in the same man- 
ner as in testing whole milk, except 
that the first whirling should be con- 
tinued for ten minutes, instead of five, 
in order to bring up all the smaller 
fat globules. The percentage of fat is 
read immediately on completing the 
final whirling. 




Fig. 66. skimmed milk test 

BOTTLE 



THE BABCOCK FAT TEST 13 

WASHING BABCOCK GLASSWARE 

Wash the glassware thoroly between each test. Any fat re- 
maining in the test bottles would increase the following test. 
First empty the contents of the test bottles on an ash heap or some 
place where the mixture will not come in contact with the food 
or the feet of animals. Do not empty the mixture into ordinary 
sinks or drains because the acid solution will destroy the sink 
and piping. Then rinse out the bottles with hot water. Add a 
strong hot solution of a good washing powder until the bottles 
are half full. Shake them vigorously while emptying them, and 
pass a small brush thru their necks; then rinse them. again using 
plenty of hot water. The bottles will then be ready to use in 
another test. 

The pipette should be rinsed out with water immediately after 
measuring out the samples, for if the milk is allowed to dry, it 
will be difficult to clean the instrument. It should also be washed 
with the hot soap solution when the bottles are being washed, 
and well rinsed afterward. 

A simple traj T for holding test bottles while carrying or wash- 
ing them is made by boring twelve or fourteen holes, to fit the 
bottoms of the bottles, nearly thru a piece of plank 12 inches long, 
6 inches wide, and 1.5 inches thick. A cover a half an inch thick 
is made with corresponding holes. The holes in the cover should 
be large enough to permit the necks of the bottles to pass thru, 
but not the bodies. 

When several bottles are to be emptied and washed, they may 
be placed in the block and the cover placed clown over them. 
By holding the block and cover together at each end, several 
bottles may be shaken or emptied as quickly as one. 

THE SPECIFIC GRAVITY OF MILK 

When equal volumes of milk and water are weighed, it will be 
found that the milk is heavier. A vessel that holds 1000 grams 
of water will hold 1032 grams of average milk ; or for each gram 
of water there would be 1.032 grams of milk. 1032 -f- 1000 = 1.032. 
Therefore 1.032 equals the specific gravity of milk since it is the 
existing ratio between the weights of equal volumes of milk and 
the standard substance water. One cubic centimeter of water 
at the proper temperature (4° C, or 39.2 ° F.) weighs one gram. 



14 TEE BABCOCK FAT TEST 

THE PIPETTE 

The Babcock pipette used in measuring milk test samples deliv- 
ers 18 grams of milk. 18 -r- 1.032 (the specific gravity of 
milk) = 17.44, the cubic centimeters of milk delivered into the 
test bottle. The pipette is made to hold 17.6 cubic centimeters 
because it has been found by experiment that the difference be- 
tween 17.6 cubic centimeters and 17.44 cubic centimeters, or 
.16 cubic centimeter, remains in the pipette. 

THE MILK TEST BOTTLE 

When the Babcock test was first invented, the scale on the 
neck of each test bottle was graduated to read from to 10 
per cent. The smallest graduations indicated .2 of 1 per cent. 
In recent years preference has been given to a test bottle that 
has a scale in which the smallest divisions indicate .1 of 1 per 
cent. The scale on this bottle reads from to 8 per cent. Both 
forms of bottles are in use at the present time. 

The graduated portion of the 10-per-cent bottle holds 2 cubic 
centimeters. One cubic centimeter of butterfat at a temperature 
of 140° F. weighs .9 of a gram. Therefore if the graduated por- 
tion of the neck of the milk test bottle were full of fat, it would 
contain 1.8 grams. That would be 10 per cent of 18 grams. 
1.8 -r- 18 = .10. .1 X 100 = 10 per cent. Eighteen grams is the 
weight of the milk placed in the test bottle. When 2 cubic centi- 
meters, the volume in the graduated part of the neck, is divided 
into ten equal parts, one part equals one per cent. 

SPECIFICATIONS AND DIRECTIONS FOR TESTING MILK 
AND CREAM FOR BUTTERFAT 

Official Dairy Instructors' Association, 1916. 
I. APPARATUS AND CHEMICALS 

Milk test bottle. — 8 per cent 18 gram milk test bottle, graduated 
to 0.1 percent. Graduation. The total per cent graduation shall 
be 8. The graduated portion of the neck shall have a length of 
not less than 63.5 mm. (2% inches). The graduation shall repre- 
sent whole per cent, five-tenths per cent and tenths per cent. 
The tenths per cent graduations shall no? be less than 3 mm. in 
length ; the five-tenths per cent graduations shall be 1 mm. longer 
tha i the tenths per cent graduations, projecting 1 mm. to the 



TEE BABCOCK FAT TEST In 

left ; the whole per cent graduation shall extend at least one-half 
way around the neck to the right and projecting 2 mm. to the 
left of the tenths per cent graduations. Each per cent graduation 
shall be numbered, the number being placed on the left of the 
scale. 

The maximum error in the total graduation or in any part 
thereof shall not exceed the volume of the smallest unit of the 
graduation. 

Neck. The neck shall be cylindrical and of uniform internal 
diameter throughout. The cylindrical part of the neck shall ex- 
tend at least 5 mm. beolw the lowest and above the highest gradu- 
ation mark. The top of the neck shall be flared to a diameter of 
not less than 10 mm. 

Bulb. The capacity of the bulb up to the junction of the neck 
shall not be less than 45 cc. The shape of the bulb may be either 
cylindrical or conical with the smallest diameter at the bottom. 
If cylindrical, the outside diameter shall be between 34 and 
36 mm. ; if conical, the outside diameter of the base shall be 
between 31 and 33 mm., and the maximum diameter between 
35 and 37 mm. 

The charge of the bottle shall be 18 grams. 

The total height of the bottle shall be between 150 and 165 
mm. (5% and 6% inches). 

Cream test bottle 1. — 50 per cent 9 gram short-neck cream test 
bottle, graduated to 0.5 per cent. Graduation — The total per 
cent graduation shall be 50. The graduated portion of the neck 
shall have a length of not less than 63.5 mm. (2y 2 inches). The 
graduation shall represent 5 per cent, 1 per cent, and 0.5 per 
cent. The 5 per cent graduations shall extend at least half-way 
around the neck (to the right). The 0.5 per cent graduations 
shall be at least 3 mm. in length, and the 1 per cent graduations 
shall have a length intermediate between the 5 per cent and the 
0.5 per cent graduations. Each 5 per cent graduation shall be 
numbered, the number being placed on the left of the scale. 

The maximum error in the total graduation or in any part 
thereof shall not exceed the volume of the smallest unit of the 
graduation. 

Neck. The neck shall be cylindrical and of uniform internal 
diameter throughout. The cylindrical part of the neck shall 
•extend at least 5 mm. below the lowest and above the highest 



16 THE BABCOCK FAT TEST 

graduation mark. The top of the neck shall be flared to a diam- 
eter of not less than 10 mm. 

Bulb. The capacity of the bulb up to the junction of the neck 
shall not be less than 45 cc. The shape of the bulb may be 
either cylindrical or conical with the smallest diameter at the 
bottom. If cylindrical, the outside diameter shall be between 

34 and 36 mm. ; if conical, the outside diameter of the base shall 
be between 31 and 33 mm. and the maximum diameter between 

35 and 37 mm. 

The charge of the bottle shall be 9 grams. All bottles shall 
bear on top of the neck above the graduations, in plainly legible 
characters, a mark defining the weight of the charge to be 
used (9 grams). 

The total height of the bottle shall be between 150 and 165 
mm. (5% and 6% inches), same as standard milk test bottles. 

Cream test bottle 2. — 50 per cent 9 gram long-neck cream test 
bottle, graduated to 0.5 per cent. The same specifications in ev- 
ery detail as specified for the 50 per cent 9 gram short-neck bottle 
shall apply for the long-neck bottle with the exception, however, 
that the total height of this bottle shall be between 210 and 235 
mm. (8Y4, and 9 inches), that the total length of the graduation 
shall be not less than 120 mm., and that the maximum error in the 
total graduation or in any part thereof shall not exceed 50 per 
cent of the volume of the smallest unit of the graduation. 

Cream test bottle 3. — 50 per cent 18 gram long-neck cream test 
bottle, graduated to 0.5 per cent. The same specifications in ev- 
ery detail as specified for the 50 per cent 9 gram long-neck bottle 
shall also apply for the 18 gram long-neck bottle, except that the 
charge of the bottle shall be 18 grams. All bottles shall bear on 
top of the neck above the graduation, in plainly legible charac- 
ters, a mark defining the weight of the charge to be used (18 
grams.) 

"Pipette, capacity 17.6 cc. of water at 20° C. Total length of 
pipette not more than 330 mm. (13^ inches). Outside diameter 
of suction tube 6 to 8 mm. Length of suction tube 130 mm. Out- 
side diameter of delivery tube 4.5 to 5.5 mm. Length of delivery 
tube 100 to 120 mm. Distance of graduation mark above bulb 15 
to 45 mm. Nozzle straight. To discharge when filled with water 
in 5 to 8 seconds. The maximum error shall not exceed 0.05 cc. 



TEE BABCOCK FAT TEST 17 

In the operation of the test the last drop of milk should be blown 
out of the pipette into the test bottle." 

Acid measure, capacity 17.5 cc. 

Cream testing" scales. Sensibility reciprocal of 30 mgm., i. e., 
the addition of 30 mgm. to the scales, when loaded to capacity, 
shall cause a deflection of the pointer of at least one division on 
the graduation. 

Weights, 9 gram weights for 9 gram cream test bottles and 18 
gram weights for 18 gram cream test bottles, preferably stamped 
correct by the United States or State Bureau of Standards. 

Tester. Standard Babcock test centrifuge and speed indicator. 

Dividers for measuring fat column. 

Water bath for cream samples, with proper arrangement for 
regulating and recording temperature of samples. 

Water bath for test bottles, of sufficient size and with necessary 
equipment to insure proper control of temperature. The follow- 
ing dimensions for a twenty-four bottle water bath are recom- 
mended : Metal box, 14 inches long, 11 inches wide and 8% inches 
deep and epuipped with a bottle basket 9% inches long and 6^2 
inches wide, capacity twenty-four bottles, a steam and water in- 
let, a drain, a thermometer holder with thermometer. 

Chemicals. Commercial sulphuric acid, specific gravity 1.82 to 
1.83 ; glymol, or white mineral oil, high grade. 

II. MANIPULATION OF TEST 
A. MiXk Test 

Milk Samples. Single samples are preferred to composite sam- 
ples. If composite samples are used they should be kept in clean 
jars sealed air-tight, and containing a sufficient amount of pre- 
servative. Corrosive sublimate, potassium bichromate and form- 
aldehyde may be used as satisfactory preservatives. For the 
keeping of composite samples a cool location should be chosen. 
They should be the product of not over one week and should be 
tested as soon as possible. 

If transported by mail, express or otherwise the sample bottle 
should be completely full and tightly stoppered and the samples 
should be preserved as above directed. 

Immediately before testing the sample is thoroughly mixed 
until it is homogeneous. If lumps of cream, butter or ice do not 
completely disappear, heat to 100° to 120° F., mix thoroughly and 



18 TEE BABCOCK FAT TEST 

pipette at once. Avoid incorporation of air bubbles while mixing 
the sample. Curdy and churned samples are not dependable. 

Testing. Measure 18 grams of milk from properly mixed sam- 
ple into standard milk test bottle, by using 17.6 cc. standard pi- 
pette; add 17.5 cc. of standard commercial sulphuric acid, and 
shake until all curd has disappeared, and then continue the shak- 
ing for a few moments longer. Milk and acid before mixing 
should have a temperature of 50° to 70°F. 

Whirl in Babcock centrifuge for five, two and one minutes, re- 
spectively, filling the bottle with hot soft water (temperature 
140°F. or above) to the bottom of the neck after the first whirling 
and to near top graduation after the second whirling. The prop- 
er speed of the centrifuge is 800 revolutions for an 18 inch diame- 
ter wheel and 1000 revolutions per minute for a 12 inch diameter 
wheel. 

Set the test bottles into water bath and read after a tempera- 
ture of 135°F. to 140°F. has been maintained for not less than 3 
minutes. Read test by measuring fat column from bottom of 
lower meniscus to top of upper meniscus. Use dividers for 
reading. 

B. Cream Test 

Cream samples. Cream samples should be tested as soon as 
possible and not later than three days after they are taken. 
Composite samples representing portions of consecutive deliver- 
ies of the same patron are unreliable. Samples should at all 
times be kept in nonabsorptive containers, sealed air-tight and 
held in the cold. 

Immediately before testing mix the sample until it pours read- 
ily and a uniform emulsion is secured. If in good condition 
shake, pour or stir until properly mixed. If very thick, warm 
to 85 °F. and then mix. In case of lumps of butter heat the sam- 
ple to 100°F. to 120°F. by setting in water bath, mix thoroughly 
and weigh out at once. For commercial work on a large scale it 
is advisable to temper all samples to 100° to 120°F. in a water bath 
previous to mixing. Great care should be exercised to avoid 
overheating the sample, causing the cream to "oil off." 
This precaution is especially necessary with thin cream. 

Testing. Weigh 9 grams or 18 grams, respectively, of the pro- 
perly mixed sample into a standard cream test bottle on standard 



THE BABCOCK FAT TEST 19 

cream testing scales which are in proper working condition, set 
level and are protected from drafts. 

Method 1. Add standard commercial sulphuric acid until the 
mixture of acid and cream, immediately after shaking, resembles 
in color, coffee with cream in it. Usually about 8 to 12 cc. of acid 
is required in the case of the 9 gram bottle or 14 to 17 cc. of acid 
in the case of the 18 gram bottle, the amount needed depending 
on the temperature of acid and cream and on the richness of the 
cream. 

Whirl in Standard Babcock centrifuge at proper speed, five, 
two and one minutes, respectively, filling the bottles with hot soft 
water, temperature 140 F. or above, to the bottom of the neck aft- 
er the first whirling and to near the top graduation after the sec- 
ond whirling. 

a. Altenate Method. Add 9 cc. of water after the cream has 
been weighed into the test bottle and before the acid is added, 
then add 17.5 cc. acid and proceed as in previous method. 
This method is applicable with the 9 gram bottle only. 

b. Alternate Method. Add 8 to 12 cc. of acid in the case of 
the 9 gram bottle or 14 to 17 cc. of acid in the case of the 18 gram 
bottle, or add acid until the mixture of cream and acid, after 
shaking, has a chocolate brown color. After the cream and acid 
have been thoroughly mixed and all lumps have completely disap- 
peared, add a few cubic centimeters (not less than 5 cc.) of hot 
soft water, whirl five minutes, add hot soft water to near top of 
scale and whirl one minute. 

The proper speed of the centrifuge is 800 revolutions per min- 
ute for an 18 inch diameter wheel and 1000 revolutions per minute 
for a 12 inch diameter wheel. 

Set the test bottles into water bath and read after a tempera- 
ture of 135° F. to 140° F. has been maintained for not less than 
three minutes, add a few drops of glymol and read at once, prefer- 
ably using dividers. Experienced testers are able to secure cor- 
rect readings without glymol by reading to the bottom of the up- 
per meniscus but the use of glymol is urged. 

C. Defective Tests 
The fat column of the finished test should be clear, translucent 
and should have a golden yellow to amber color. All tests which 



20 TEE BABCOCK FAT TEST 

are milky, or foggy, or showing the presence of curd or charred 
matter in or below the fat column, or of which the reading is in- 
distinct or uncertain, should be rejected. Duplicate tests are es- 
sential in all work where special accuracy of results is required, 
such as official testing and experimental investigations. 



EXERCISES 

PART I 



22 DAIRY LABORATORY EXERCISES 

EXERCISE I 
THE BABCOCK TEST 

Special directions should be given to students by the instructor 
as to handling materials used in testing, laboratory technique and 
running the different centrifuges. 

All glassware should be thoroughly cleaned before beginning 
the practice. 

1. Test for fat by the Babcock method a sample of whole milk 
and a sample of skimmed milk. 

2. Take the temperature of the milk before adding the acid. 
Take the temperature of the acid before adding it to the milk. 
Take the temperature of the mixture of acid and milk immediate- 
ly after mixing. Complete the test record all readings of tem- 
peratures and fat percentages. 

3. Using water in place of milk repeat the experimeni up to the 
operation of centrifuging the bottles. 

QUESTIONS 

Note the weight of the volume of acid used as compared to the 
weight of the same volume of water. Note the color of the mix- 
ture in the bottle after the acid has been mixed with the milk. 

Note the color of the fat in the completed test. 

Note the graduations on the pieces of glassware used. Record 
all data. 

Write a complete description of the Babcock test for fat in milk 
and skimmed milk. 

Record at least five references on the Babcock test. 



DAIRY LABORATORY EXERCISES 23 



24 DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 25 

EXERCISE II 

CONFORMITY OP BABOOOK G-LASSWAKE TO SPECIFICATIONS 

I. Compare the measurements of one milk test bottle, one 
cream test bottle and one pipette with specifications, using a rule 
graduated in the metric system. 

II. Make drawings of the above named pieces of apparatus 
and indicate measurements. 

III. Using an alcoholic solution made by adding 10 cc. of 
alcohol to 90 cc. of water colored red with alkanet root, deter- 
mine the capacity of the graduated neck of a ten per cent milk 
test bottle as follows : Fill the bottle to the zero graduation 
with water at room temperature. Fill an accurately graduated 
10 cc. burette to the zero mark with the colored solution. Dry 
the neck of the test bottle by the use of narrow strips of blotting 
paper. Run the colored solution from the burette into the bottle 
neck, taking readings at each per cent graduation. Each per 
cent graduation should equal .2 cc. of the colored solution. 

IV. Following the same directions determine the accuracy of 
calibration of an eight per cent milk test bottle, a six inch cream 
test bottle and a nine inch cream test bottle. 

QUESTIONS 

How would large variations in the diameters of the bore in 
different milk test bottles affect the accuracy of the fat per- 
centage reading? 

Give the legal requirements covering the use of Babcock glass- 
ware in your state. 

What is the maximum error in the graduations on test bottles 
permitted by the specifications for Babcock glassware? 

Name the apparatus and chemicals used in the Babcock test 
for which specifications are given by the Am. Dairy Sci. Ass. 

Give the specification for chemicals. 



26 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 27 



28 DAISY LABORATORY EXERCISES 

EXERCISE III 
ACCURACY OF CALIBRATIONS AND SPEED OF CENTRIFUGE 

1. Fill a Babcock pipette to the graduation with water at a 
temperature of 60° F. Accurately weigh the amount of water 
it delivers. 

Fill the same pipette with milk at 60° F. and accurately weigh 
the amount of milk it delivers. 

In each case note the time required for the contents of the 
pipette to be delivered. 

2. Using the Nans bottle tester determine the accuracy of 
the graduations of one milk test bottle and one cream test bottle. 

3. On a steam centrifuge determine the number of pounds of 
steam pressure, as indicated by the steam gauge, that will cause 
the disc to revolve (a) 800 revolutions per minute, (b) 1000 
revolutions per minute for each steam centrifuge in the lab- 
oratory. 

(See Farrington & Wall.) 

QUESTIONS 

1. Why is temperature of importance in determining the 
weight of definite volumes of liquids? 

2. Why is there a difference in weight between equal volumes 
of milk and water? 

3. In experiment I was there a difference in the length of 
time required for the milk and water to flow from the pipette. 
If so what caused this difference? 

4. Give the precautions to be observed in using a Nans bottle 
tester. 

5. In steam centrifuges of the same size and style why may 
the pounds of pressure on the different steam gauges vary when 
all of the disks are revolving at the same speed. 

6. Derive a formula for determining the speed of the disk 
of a Babcock centrifuge. 

7. Define centrifugal force. 

8. Why does the specific gravity of sulphuric acid vary? 

9. Give the commercial name and the physical and chemical 
properties of sulphuric acid. 

10. What is the relation between speed, centrifugal force and 
the diameter of the disc in the operaiton of the Babcock test? 



DAIRY LABORATORY EXERCISES 29 



SO DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 31 

EXERCISE IV 

TESTING SKIM MILK AND CREAM 

1. Test by the Babcock method a sample of whole milk, 
skimmed milk and cream. 

2. Weigh into a convenient dish 20 grams of the cream just 
tested and add to it 18 grams (one pipette full) of the milk. 
Compute the percentage of fat in this mixture and verify your 
results by testing the sample in a cream test bottle. 

3. Place 36 grams (two pipette fulls) of the milk used in 
experiment one in a convenient dish. Add to this 18 grams 
(1 pipette full) of the skimmed milk used in experiment one. 
Compute the percentage of fat in this mixture and verify your 
results by testing the sample in a milk test bottle. 

QUESTION'S 

1. Give the precautions that must be taken in preparing 
samples of milk and cream for testing. 

2. (a) Name the different steps in making a Babcock test of 
milk. 

(b) Of Cream. 

Note : Reasons for methods not required here. 



32 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERi 1SES 






34 DAIRY LABORATORY EXERCISES 

EXERCISE V 

MODIFYING TESTS 

1. Test for fat by the Babcoek method a sample of whole milk, 
skimmed milk and cream in the usual way. 

2. Retest the skimmed milk and cream. 

In' retesting the skimmed milk use the same amount of acid 
as for whole milk (17.5 cc.) and centrifuge five, two and one 
minutes. 

In retesting the cream do not add water to the cream before 
adding the acid. 

3. Retest the cream. 

In retesting the cream measure it with the pipette instead of 
weighing it. 

Compare the results obtained by measuring and weighing the 
sample. 

QUESTIONS 

1. Which is heavier — cream containing a high percentage of 
fat or cream containing a low percentage and why? 

2. By a diagram and written description explain how to read 
a Babcoek fat test (a) of milk; (b) of cream. 

3. Explain why the method differs for reading the two tests. 

4. Describe how to make meniscus remover. 

5. Why is cream weighed into the test bottle in place of 
measured in making the Babcoek test? 

6. What is the purpose of placing water in the cream test 
bottle before adding the acid? 

7. What is "meniscus remover" and why is its use necessary? 

8. How does the fat in skim milk compare with the fat in 
whole milk? 



DAISY LABORATORY EXERCISES 35 



36 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 37 

TESTING BUTTER FOE MOISTURE 

Practically the only volatile substance in butter is the water. 
It may be all driven off by heating to 100° C. for a sufficient 
length of time, care being taken not to overheat or char any 
of the other constituents. A number of moisture tests have been 
developed and most of them are carried out approximately on 
the principle of the Patrick butter moisture test, which was one 
of the earliest developed. 

Operating the test: A representative sample of the butter is 
mixed until it is of a homogenous mass. Ten grams of the pre- 
pared butter are then weighed out in an aluminum cup. The cup 
is then heated over a flame. Prof. Eoss in the Cornell Butter 
moisture test advises the use of an asbestos pad to be placed 
between the flame and the cup containing the butter. The cup 
should be shaken while heating by holding it with the hot pan 
lifter and giving it a rather vigorous circular motion. Each 
speck of casein has a white color until it loses its mosture ; 
therefore, heating is continued until the last white particle has 
changed to a light brown color. 

When the moisture is all driven off as indicated by the color 
of the casein, the cup is covered and allowed to cool to room tem- 
perature in a clean dry place. When cooled it is again weighed 
and the loss in weight divided by the weight of butter placed in 
the cup. The quotient multiplied by 100 gives the percentage of 
moisture in the butter. 



38 DAIRY LABORATORY EXERCISES 

EXERCISE VI 

BABCOCK TEST, BUTTEB MOISTURE TEST AND COMPOSITE 
SAMPLES 

1. Test for fat by the Babcock method a sample of buttermilk, 
chedclar cheese and whey. 

2. Test for fat each of the five samples of milk furnished. 
Place in a lightning top sample jar an aliquot sample from each 
of the five samples just tested. Add a preservative and hold for 
future testing. Record the number of cc. in each bottle of milk 
sampled. 

3. Test a sample of butter for moisture by the Cornell method. 

QUESTIONS 

1. Describe the condition of the water in butter (a) when the 
sample is taken (b) after properly preparing the sample for 
making a moisture test. 

2. How may we know when all of the moisture has been 
driven from a butter sample and what causes this change? 

3. Why is it necessary to use different amounts of sulphuric 
acid in testing different dairy products for fat? 

4. How does whole milk cheese, part skimmed cheese andi 
full skimmed cheese differ in composition? 

5. Give the only advantage, in taking milk samples, that a 
milk sampling tube has over a small dipper. 



DAIRY LABORATORY EXERCISES 39 



40 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 41 

THE SPECIFIC GBAVITY OF MILK AND THE USE OF THE 
LACTOiMETEE 

The specific gravity of a substance may be defined as the 
weight of unit volume of that substance as compared to the 
unit volume of some other substance which is taken as a standard. 
Water is taken as the standard for all liquids and it has a specific 
gravity of one. Milk varies in specific gravity from 1.029 to 
1.035, the average specific gravity being 1.032. 

The instrument used for determining the specific gravity of 
liquids is called a hydrometer, and there are many kinds of 
specialized hydrometers, one of which is called a lactometer. The 
lactometer is an instrument used to determine the density of 
milk. There are two general types of lactometers in use in this 
country: the Quevenne and the New York State "Board of Health 
or ordinary lactometer. The latter is commonly called the B. of 
H. lactometer. 

A Lactometer consists of a hollow glass cylinder drawn to a 
long narrow stem at one end and a weighted bulb at the other. 
On the stem is a scale which gives the density of the milk. The 
weight consists of shot or mercury. The weight makes the instru- 
ment take an upright position in the liquid and also locates the 
position of the hydrometer scale in the stem. The higher priced 
instruments contain a thermometer. The thermometer bulb con- 
taining the mercury is annealed in the instrument over the 
hydrometer bulb and the thermometer stem passes up thru the 
body and stem of the lactometer. The thermometer scale appears 
on the opposite side of the stem from the hydrometer scale or 
over it. 

The Quevenne lactometer is an instrument graduated from 
15° — 40° corresponding to specific gravities of 1.015 — 1.040. The 
chief advantage of the Quevenne lactometer is that it reads the 
specific gravity of milk directly by placing the figures 1.0 before 
the lactometer reading. (Example: Lactometer reading — 32. 
The specific gravity— 1.032.) 

The Board of Health lactometer is the same as the Quevenne 
lactometer with the exception of the lactometer scale. If the 
Quevenne scale were put in a suitable B. of H. lactometer you 
would have a Quevenne lactometer. The B. of H. scale extends 
from 0° to 120° and there are sixty divisions each equalling two 



42 DAIRY LABORATORY EXERCISES 

on the scale. A reading of 100 on the B. of H. scale corresponds 
to a reading of 29 on the Quevenne scale. 

One degree on the Quevenne equals 3.44 on the B. of H. 
(100 -=- 29 = 3.44.) To convert from B. of H. reading to 
Quevenne reading you multiply the B. of H. reading by .29 and 
to convert from Quevenne reading to B. of H. reading you divide 
by .29. 

Average quality milk reads 32 on the Quevenne scale but pure 
milk readings vary between 29 and 35. Average quality milk 
reads 108 to 110 on the B. of H. scale but pure milk reading 
may vary between 100 and 115. 

Temperature corrections for the lactometer : It is a well known 
fact that volume and density are affected by temperature. As 
the temperature rises the volume increases and the density de- 
creases and as the temperature falls the changes occur in the 
opposite direction. A 10° temperature change equals 1° on the 
Quevenne lactometer scale and 3° on the B. of H. lactometer 
scale, or 1° temperature change equals .1 of a lactometer degree 
on the Quevenne scale and .3 of a lactometer degree on the 
B. of H. scale. The lactometer reading should be taken at a 
temperature near 60° F. as the temperature correction factor 
varies when too far away from this figure. If the temperature of 
the milk is below 60° F. subtract the correction factor and if 
the temperature is above 60° F. add the correction factor. 

FORMULAS FOR CALCULATING SOLIDS NOT FAT 

When the Quevenne lactometer reading and the per cent of 
fat in a sample of milk are known the per cent of solids not fat 
may be calculated by formulas. A great many formulas have 
been developed but the following formulas developed by Babcock 
are most generally used. 

1. L + .7F 

= s N F 

3.8 Dp *■ 

. 2 ' j-+ .2F + .14 = S. N. F. 

3 ' \ 1- .2F = S. N. F. 

4 ' 

L = Lactometer reading (Quevenne) 

F = The per cent of fat. 



DAIRY LABORATORY EXERCISES 43 

Formula 1 gives the best results when uesd on rich milk. 
Formula 2 is used with average milk. 
Formula 3 is used with milk poor in fat. 

Another formula developed by one of the authors is as 
follows : 
L + F 
4 
This formula gives good results with average quality milk and 
milk rich in fat. It gives results a little too high for milk poor 
in fat. 

Another formula developed by one of the authors where 
the B. of H. lactometer reading is used, is as follows : 

lL-8 + I-an.F. 

L = The B. of H. lactometer reading. 
F = The per cent of fat. 

This formula gives good results with average milk and milk 
rich in fat but a little to high for milk poor in fat. 

CALCULATING MILK ADULTERATIONS EBOM THE LACTOMETER 
READING AND THE PERCENT OF FAT IN THE SAMPLE. 

Example — A sample of normal milk had a lactometer reading 
of 32 @ 64° F. and a fat content of 4%. After being adulterated 
both by watering and skimming it showed a lactometer reading 
of 25 @ 50° F. and a fat content of 2.8%. Figure out the per cent 
of fat removed by skimming and the per cent of fat removed by 
watering. 

Use the formula L -4- F 

Correcting for temperature: 32 @ 64° F = 32.4 @ 60° F. 
32,4 + 4 = 9.1% S. N. F. in the normal milk. 

The adulterated milk had a lactometer reading of 25 @ 50° F. 
and correcting for temperature it would be 24 @ 60° F. 

24 + 2 ' 8 = 6.7% S. N. F. in the adulterated milk. 
4 

Since there were 9.1 parts of S. N. F. before adulteration and 



44 DAIRY LABORATORY EXERCISES 

6.7 parts of S. N. F. after adulteration 2.4 parts were removed 
by adulteration. 

9.1 — 6.7 = 2.4 

2.4 -=-9.1 = .2417 X 100 = 24.17 % of the 8. N. F. removed 
by watering. 

Before adulteration the sample had 4 parts of fat and after 
adulteration 2.8 parts of fat ; 1.2 parts of fat were removed. 

4 — 2.8= 1.2 

1.2-^4= .3 X 100 = 30% 

Therefore 30% of the total fat has been removed. When water 
is added to milk all of the solids are reduced in the same propor- 
1 ion. 

It was shown that 24.17% of the solids not fat were removed by 
watering, therefore 24.17 per cent of the fat were removed by 
watering according to the above rule. 

The total fat loss was 30%. Therefore the difference between 
30% and 24.17 = 5.83% which was removed by skimming. 



DAIRY LABORATORY EXERCISES 45 

EXERCISE VII 

EFFECT OF TEMPEKATUKE AND DIFFERENT AMOUNTS OF ACID 
AND USE OF QUEVENNE LACTOMETER 

1. Test in duplicate by the Babcock method a sample of whole 
milk as follows : 

(a) Use ordinary amount of acid. 

(b) Use one-half the usual amount of acid. 

(c) Fill the bottle to the base of the neck with acid. 

(d) Use the regular amount of acid, but warm the acid and 
milk to 100° F. (before mixing) 

Add the acid slowly to the sample. 
Observe and record all results carefully. 

2. Test the sample preserved from the last exercise. Allowing 
each cc. of milk in each quantity of milk sampled to represent 
one pound of milk, calculate the theoretical per cent of fat in 
the preserved sample. 

Compare results with the actual test of the composite sample. 

3. Take the Quevenne reading of a sample of milk at 60° F. 
Warm the milk up to 100° F., recording the lactometer reading 
at each 10° rise in temperature. Cool the milk as low as possible, 
recording the lactometer reading at each 10° drop in temperature. 

Note. Remove the lactometer and mix the milk thoroughly 
before each reading. 

Compare the readings with those obtained with the lactometer 
by applying the correction factor for temperature. 

Make a drawing of the Quevenne lactometer, labelling each 
part and state the purpose of each part. 

QUESTIONS 

1. Why is the Babcock test not reliable for determining the 
percentage of fat in butter? 

2. Why and how does a change in the temperature of the 
milk affect the lactometer reading? 

3. Give the precautions that must be taken in holding com- 
posite samples for testing. 

4. Why should a composite sample be made up of aliquot 
portions of each mass of milk sampled? 

5. Define Specific Gravity. 



46 DAISY LABORATORY EXERCISES 

6. Explain why and how varying the amount and the tem- 
perature of the acid used affects the fat column in the com- 
pleted test. 

7. Give the precautions that must be taken to insure proper 
action by the acid in testing dairy products. 

8. Was there any indication that the preservative in the 
composite sample affected in any way the appearance or reading 
of the test? 



DAI BY LABOEATOBY EXERCISES 



48 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 49 

EXERCISE VIII 
COMPOSITION OF MILK AND TEST FOE BOILED MILK 

1. Test a sample of whole milk and skimmed milk for fat 
by the Babcock method. 

Take the Quevemie and B. of H. lactometer readings of the 
milk and skim-milk. Convert the B. of H. lactometer reading to 
the Quevenne reading and compare the result with the actual 
reading obtained with the Quevenne lactometer. 

Compute the S. N. F. in the whole milk by using three different 
formulae and compare results obtained. 

2. Measure out in duplicate into two cream test bottles a 
sample of skimmed milk as for the Babcock test. Before adding 
the sulphuric acid dip a stirring rod into the formaldehyde and 
rinse it off in one of the samples. Then add to both samples the 
ferric chloride and the sulphuric acid and note the difference in 
color due to formaldehyde. 

3. Test for formaldehyde any four of the samples furnished. 
Report the results by number. 

4. Place into each of two whole milk bottles a sample of boiled 
milk. Number the bottles one and two. Into each of two whole milk 
bottles place a sample of raw milk. Number the bottles one-A 
and two-A. 

A. Test for boiling bottle number one of the boiled milk and 
bottle number one-A of the raw milk. Use the calcium peroxide 
and the paraphenylene diamine-hydrochloride. 

B. Test for boiling, bottle number two of the boiled milk and 
bottle number two-A of the raw milk. Use the calcium peroxide, 
the potassium iodide solution and the starch solution. 

QUESTIONS 

1. ' Can pasteurized milk be distinguished from raw or boiled 
milk by the boiled milk test ? 

2. Upon what principle does the boiled milk test depend? 

3. Why does sulphuric acid alone sometimes give the for- 
maldehyde test? 

4. Is it legal to use formaldehyde as a milk preservative? 
Give its relative merits as a milk preservative. 



50 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



52 DAIRY LABORATORY EXERCISES 

EXERCISE IX 

BADCOCK TEST AND CALCULATING ADULTERATION 

1. Test for fat by the Babcock method a sample of whole milk, 
cream and a sample of skimmed milk. 

Take the Quevenne lactometer reading of both the whole milk 
and the skimmed milk. 

2. Place in the lactometer cylinder 100 cc. of the whole milk 
and 75 cc. of the skimmed milk. Mix thoroughly and again take 
a lactometer reading and make a fat test of the mixture. Then 
add to the mixture of whole milk and skimmed milk 25 cc. of 
water. Mix well and again take a lactometer reading and make 
a fat test. Compute the percentage of fat removed by skimming 
and the percentage of fat removed by watering and the total 
fat loss. 

3. (a) To 200 cc. of the skimmed milk used in experiment one 
add 25 cc. of the cream used in experiment one. Mix thoroughly 
and take a lactometer reading. Make a fat test and calculate 
the effect on both the Board of Health and Quevenne lactometer 
reading of one per cent increase of the fat, 

(b) Take a lactometer reading of a sample of water. To 200 
cc. of the water add 100 cc. of the skimmed milk. Again take 
a lactometer reading of the mixture and calculate the effect of 
one per cent of solids not fat on the lactometer reading. Use 
both the Quevenne and the Board of Health lactometers. 

QUESTIONS 

1. Why does whole milk and skimmed milk differ in specific 
gravity ? 

2. What is the difference in effect of one per cent of fat and 
one per cent of solid not fat on (a) the B. of H. lactometer 
reading; (b) on Quevenne lactometer reading; (c) on the specific 
gravity ? 

3. What is the difference in effect on the physical properties 
and composition of whole milk when water is added and when 
skimmed milk is added? 

4. Give the composition of the milk from four of the principal 
breeds of dairy cattle. 



DAIRY LABORATORY EXERCISES 53 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 55 

REASONS WHY MILK GIVES AN ACID REACTION 

1. Milk contains substances that cause that which is called 
the apparent acidity. These substances are the acid phosphates, 
the casein which will take up some alkali, and the carbon dioxide 
that may be in solution in the milk. 

2. The real acidity is due to the lactic acid, or to the casein 
freed by the acid uniting with the calcium in the milk. 

The presence of real acidity or lactic acid in the milk is due 
to the action of lactic acid organisms (or germs) on the milk 
sugar. 

C 12 H 2 Ai + H 2 = 4 C 3 H 6 3 

There are two theories in regard to the actual formation of 
the acid. 

1. That the germs produce an enzyme which acts upon the 
milk sugar and produces an acid. 

2. That the germs produce the acid by acting directly on the 
sugar. This last theory is the one generally accepted. The 
apparent acidity usually does not go above .18 per cent, but may 
go to .25% calculated as lactic acid. .05 to .10% of real acidity 
in milk can be detected by the sense of smell. .10% to .15% of real 
acidity in milk can be detected by taste. .58% of acid will 
produce coagulation at ordinary temperatures. When .8% of 
lactic acid has developed in milk the germs cease to produce more. 

In the acid test, the acid is measured by adding two or three 
drops of an indicator (phenolphthalien) to a known weight of 
the milk and then running in from a graduated burette, an alkali 
solution of known strength until the milk turns pink. When the 
solution turns pink we know that all the acid has been neutralized 
and the percentage of acid may be calculated. Equal volumes 
of acid and alkali solutions of the same strength will neutralize 
each other. 

In preparing solutions for determining the percentage of acid 
or alkali in other solutions, there must be a standard of strength 
to Avork by and this standard is the normal solution. 

A normal solution contains in one liter one gram of replaceable 
hydrogen or its chemical equivalent. Therefore one cc. of a nor- 
mal solution of an acid will be neutralized by an equal volume of 
a normal solution of an alkali because they contain amounts of 
the reagents that are chemically equal. And one cc. of a normal 



56 DAISY LABORATORY EXERCISES 

solution would neutralize .09 grams of lactic acid as that is the 
amount which one cc. of a normal solution of lactic acid contains. 

Since more accurate work can be done with weak solutions, it 
is customary to use those of tenth normal strength, written N/10 
One cc. of a N/10 solution of an alkali will neutralize .009 grs. of 
lactic acid. 

To determine the per cent of acid in the milk, multiply the 
number of cc. of N/10 alkali used to neutralize a known weight 
of the milk by .009 and divide by the weight of milk taken. If 
the milk was measured out for titration, it should be changed 
to grams by multiplying the number of cc. used by the specific 
gravity. 

THE ACIDITY OF MILK 
When the chemical properties of substances are studied it is 
found that a number have opposite characteristics and that many 
substances can be placed in one or the other of three classes. 
These classes are acids, alkalies and salts. The acids and bases 
when brought together always tend to neutralize each other 
forming new substances that are called salts. The salts do not 
possess the characteristic properties of either the acids or the 
alkalies. It is often necessary to determine whether substances 
have acid or alkali properties and this is done by using reagents 
that are called indicators. There are many kinds, but the indi- 
cator generally used in acid tests of milk is named phenol- 
phthalein. It is colorless in acid solutions and purple or pink in 
alkaline solutions. It is important to know the acidity of the 
milk for the following reasons : 

1. In the ripening of cream, unless sweet butter is to be 

manufactured. 

2. In the making of cheese : when to add the rennet, when 

to draw off the whey, when to mill the curd, etc. 

3. Sometimes of value in market milk work in determining 

whether a certain mass of milk is fit to send to the 
market. 

4. When condensing milk it enables the man on the re- 

ceiving platform to select the milk that is not too sour 
and reject milk that has developed more than .2% acid. 

5. In making sour milk beverages. 

6. Manufacturing of casein. 



DAISY LABORATORY EXERCISES 57 



ALKALINE TABLET SOLUTION 



Professor Farrington of the University of Wisconsin devised 
alkaline tablets to be used in determining the percentage of 
acid in milk. These tablets are -made up so that each will neutral- 
ize .03492 grams of lactic acid. When five tablets are dissolved 
in 97 cc. of water the solution is of such strength that one cc. of 
it will neutralize .01 of one per cent of lactic acid when 18 grs. 
(1 pipette full) of milk are taken. The solution should not be 
allowed to stand uncorked. The indicator is added to the tablets 
when they are manufactured, therefore it enters the milk with 
the alkali tablet solution and no more indicator (phenolphthalein) 
need be added. The following example shows how these tablets 
are used. 

Suppose that it required 15 cc. of an alkali tablet solution to 
neutralize the acid in 18 grs. of milk. The tablet solution was 
made by dissolving 7 alkali tablets in 100 cc. of water. What is 
the per cent of acid in the milk? 

One tablet will neutralize .03492 grs. of lactic acid. 

.03492 X 7 = .24444 grams of lactic acid that seven tablets 
will neutralize, 

Since the seven tablets were dissolved in 100 cc. of water, the 
entire 100 cc. of the solution would neutralize .24444 grams of 
latcic acid. Then .24444 -±- 100 = .0024444 the grams of lactic 
acid that one cc. of the solution will neutralize. 

.0024444 X 15 (cc. used) = .036666 grams of acid neutralized. 
.036666 -f- 18 = .002039 X 100 =. .2039% 



58 DAIBY LABORATORY EXERCISES 

EXERCISE X 

BABCOCK TEST, ACID TEST AND DENSITY 

1. Test the skimmed milk for acid using tenth-normal alkali 
solution and a Farrington alkali tablet solution. 

2. Test for acid 17.6 cc. of tap water (1 pipette full). Add 
to a pipette full of the water 5 cc. of starter or buttermilk. Again 
test for acid using the tenth-normal alkali solution. 

3. Test for fat by the Babcock method a sample of whole milk 
and a sample of butter. 

4. Take both the Quevenne and the Board of Health lacto- 
meter readings of a sample of whole milk and make the necessary 
temperature corrections for the lactometer readings. 

Add 50 cc. of water to 200 cc. of the milk and take the lacto- 
meter reading. Use both lactometers. Calculate the percentage 
of water that would cause the lowering of the lactometer reading 
one degree. 

Add a gram of salt to the solution and again take both lac- 
tometer readings. Calculate the percentage of salt that would 
cause the raising of the lactometer reading one degree. Use 
both lactometers. 

5. Determine the acidity of a sample of fresh milk using the 
tenth-normal alkali solution. Divide the milk into two portions. 
Calculate the amount of buttermilk that must be added to one 
portion of the fresh milk to increase the acidity .02 per cent. 

Add the required amount of buttermilk to this portion of the 
fresh milk. Make a determination of the increased acidity in the 
mixture by titrating with tenth-normal alkali. 

6. Place 2 cc. of each sample into each of two test tubes and 
have both at a temperature of from 60° — 70° F. Add to each, 2 
cc. of a 68% alcohol solution, shake with a circular motion to 
mix thoughly. Then shake the tube to splash some of the mixture 
against the wall of the tube an inch or more above the surface of 
the liquid. 

The presence of lactic acid in the milk will be shown by small 
flakes of casein deposited on the wall of the test tube above the 
surface of the milk. 



DAIRY LABORATORY EXERCISES 59 



QUESTIONS 

1. Why was there a demand for an alkali tablet solution in 
place of a tenth-normal alkali solution? 

2. What is "starter" and for what is it used? 

3. Why was there a demand for the alcohol test in determin- 
ing milk quality? Upon what principle does it depend? 

4 Explain the differences between a normal solution, a stan- 
dard solution and a saturated solution. 



DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 



62 DAIRY LABORATORY EXERCISES 



CHEESE MOISTURE TEST 



Laws enacted recently by various States limiting the amount of 
water permissible in cheddar cheese have created a demand for 
a practical cheese moisture test. The ordinary butter moisture 
rest, in which a metal cup is heated over a flame, cannot be used 
for determining the percentage of water in cheese because the 
high temperature developed in operating that test drives off from 
the cheese other substances with the water. Also, particles of 
cheese are lost by spattering when the cheese is heated with any 
degree of rapidity in the shallow butter-moisture cups. 

To overcome these difficulties the new method here described was 
developed by one of the authors for the purpose of determining 
J .he percentage of moisture in cheese. The apparatus used in the 
new test consists of: 

1 double-walled copper drying cup 

1 centigrade thermometer registering to 200° 

1 alcohol lamp 

1 tripod 

1 special flask 

1 scales sensitive to 0.01 gram 

1 set of weights, 0.01 to 100 grams. 

Operating the test: In operating the test the alcohol lamp is 
first ligthed, so that the oil bath may be warming while the test 
sample is under preparation. A representative sample of the 
cheese, which may be taken with a cheese trier and held in a 
glass-stoppered sample jar, is then cut into particles about the 
size of kernels of wheat without removing it from the jar. This 
may be done with an ordinary table knife that has had the end 
squared and sharpened. The clean dry flask is then accurately 
balanced on the scales and a 5-gram weight is placed in the oppo- 
site scale pan. Particles of cheese from the prepared sample are 
put into the flask until the scales comes to an exact balance. 
Great care should be taken to avoid. loss of moisture from the 
cheese during the preparation of the sample. 

With the thermometer in the oil bath registering a temperature 
between 140° and 145° C. (or between 284° and 293° F.), the flask 
is placed in the cup of the oil bath and the flat, disk-shaped cover 
is adjusted over the apparatus. The flask should remain in the 
bath for fifty minutes, the temperature being kept between 140° 
and 145° C. all the time. The flask is then removed, covered, and 



DAISY LABORATORY EXERCISES 63 

allowed to cool to room temperature in a dry place. It is then 
weighed, and the quotient obtained by dividing the loss in weight 
by the original weight, multiplied by 100 gives the percentage of 
water in the cheese. The following shows the method of com- 
putation : 

Problem: Five grams of cheese was heated until the water 
contained in it was evaporated. The remaining substance weighed 
3.15 grams. What percentage of water did the cheese contain? 

Answer: 5.00 — 3.15 = 1.85 
1.85 -=- 5 = 0.37 
0.37 X 100 = 37 (percentage of water in cheese) 

A butter moisture scales with an extra 5-gram weight may 
be used for weighing out the 5 grams of cheese. If the scales 
indicates the amount of moisture in 10 grams of butter by per- 
centage graduations on its beam or by percentage weights, then 
it will be necessary to multiply by two the percentage indicated 
by such scales or percentage weights when only 5 grams of cheese 
is used. 



DAI BY LABORATORY EXERCISES 



EXERCISE XI 

CHEESE MOISTURE TEST, BABCOCK TEST, ACID TEST AND 
LACTOMETER 

1. Test a sample of cheese for moisture by the Cornell method. 

2. Test for fat by the Babcoek method a sample of cheese, 
whole milk and a sample of cream. 

3. Test for acidity a sample of milk and a sample of cheese. 

4. Take the lactometer reading of the whole milk and com- 
pute the total solids using all three formulae. 

QUESTIONS 

Why cannot cheese be tested for moisture in the same way 
as butter is tested for moisture? 

To what is the high acid content of cheese due? 



DAIRY LABORATORY EXERCISES 65 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 67 



SALT IN BUTTER 



The percentage of salt in butter varies to a greater extent than 
any other constituent. Salt is added to butter to assist in remov- 
ing the butter milk to improve the keeping quality and give an ac- 
ceptable flavor. Usually more than one per cent and less than 
four per cent of salt is left in the butter after the working process 
is completed. The amount of salt left in the butter may depend 
upon the demand of the trade supplied or upon the methods and 
skill of the butter maker. 

The best way to learn how to control the per cent of salt is to 
make salt tests of the finished product from day to day and note 
the effect of the various conditions connected with the churning 
and the working process upon the per cent of salt retained. The 
salt should always be in solution and it is held in solution by the 
water that is in the butter. The lower the water content of the 
butter the lower would be the per cent of salt that would be held 
in solution. Thus a sample of butter that contained 14% of 
moisture and 3% of salt would not be so liable to have salt crys- 
tals deposited as would a sample that contained 3% of salt and 
only 10% of moisture. The difference in taste of butter contain- 
ing 2% of salt and butter containing 3% of salt is marked, but the 
taste will distinguish very little difference betwen butter contain- 
ing 5% of salt and another sample containing 8% of salt. This 
is due to the fact that the final taste on the tongue is due to pure 
salt in each case. 

TESTING BUTTER FOR SALT 

One of the authors developed the following test in 1908 to sup- 
ply the demand of butter makers for a simple, 'accurate and prac- 
tical method to determine the per cent of salt in their product. 
Apparatus. 

One ten cc. buretle graduated to tenths of a cc. 

Babcock milk pippette. 

One white cup. 

One pint bottle marked to show the line at the upper surface of 
the liquid when the bottle contains 300 cc. 

Reagents. 

Standard tenth normal silver nitrate soluion (AgN0 3 ) 

Ten per cent potassium chromate solution. (K 2 Cr0 4 ) 



68 DAIRY LABORATORY EXERCISES 

The test is performed as follows : A homogeneous sample of 
the butter is prepared in the same way as for the butter fat or 
butter moisture test. Weigh ten grams of the prepared sample 
into a suitable dish. Or if a moisture test was made on ten grams 
of butter, that remaining in the cup when it is finally weighed may 
be used. Wash the butter from the cup into the bottle marked at 
the 300 c.c. point. Make certain that no salt remains in the cup 
and use water sufficiently hot to readily melt the butter. Usually 
about 200 cc. is used for this purpose. Next add enough hot wa- 
ter to bring the surface of the water on a level with the line at the 
300 cc. mark. The melted butter fat floating on the surface of 
the water should then be above the 300 cc. line. Place the stop- 
per in and shake the bottle vigorously for about a minute. That 
will enable the water to dissolve all of the salt and wash it out of 
the fat. Let the bottle remain quiet for about five minutes until 
most of the fat has risen to the surface. Then draw a Babcock 
pipette full to the mark (17.6 cc.) of the water portion and place 
it in a white cup. Add three or four drops of the potassium chro- 
mate solution, stir, and run in the standard silver nitrate solution 
from the burette, with constant stirring until the yellowish solu- 
tion in the cup takes on a permanent light brownish tinge of col- 
or. Then read on the burette scale the number of cc. of the stand- 
ard tenth normal silver nitrate solution used. Each cc. of the 
tenth normal silver nitrate solution used equals one per cent of 
salt in the butter. In adding the silver nitrate solution care 
should be taken to not run in any more than enough to cause the 
first permanent brownish color to appear. A deep brown color 
indicates that a little more of the silver nitrate solution was run 
in than was necessary. 



DAISY LABORATORY EXERCISES 



EXERCISE XII 



BABCOCK TEST, USE OF HAND MACHINE, ACID TEST, BUTTEB 
MOISTURE AND SAiLT TEST 

1. Test for fat by the Babcock method in the steam machine a 
sample of whole milk, skimmed milk and cream. 

Retest the whole milk in the hand machine and compare- the 
results with those obtained in the steam machine. 

2. Test for acid a sample of whole milk, cream and skimmed 
milk using both the tenth-normal alkali solution and a Farrington 
alkali tablet solution. 

3. Test a sample of butter for moisture and salt using the Cor- 
nell method in each test. 

1. What special precaution must be observed in using a hand 
machine for determining the fat content of milk? 

2. Prove by a numerical problem that the Cornell Salt test for 
salt in butter is correct. 



DAIRY LABOR ATOEY EXERCISES 



DAIRY LABORATORY EXERCISES 71 



72 DAIRY LABORATORY EXERCISES 



EXERCISE XIII 

MICROSCOPICAL APPEARANCE OP MILK, USE OF RENNET, SALT 
TEST, BABCOCK TEST 

1. Examine under the high power microscope a sample of 
whole milk, skimmed milk and cream. 

Make drawings of each field. 

2. Take 18 grams of milk at 50°F and add four drops of ren- 
net, shake thoroughly and let stand. 

Note the length of time it takes the milk to curdle. 
Repeat at temperatures of 80°F, 100°F, 150°F. 

3. To 100 cc. of water add lcc. of sulphuric acid. Add one cc. 
of this solution to 18 grs. of milk and add 4 drops of rennet at 
50°F, 80°F, 100°F and 150°F. Note the time it takes the milk to 
coagulate. Compare the length of time with that required in No. 2. 

4. Test for fat by the Babcock method a sample of evaporated 
milk. 

5. Test for salt a sample of butter. 

QUESTIONS 

Give the reasons for all the differences in appears ices between 
the field of cream, whole milk and skim milk examined under the 
microscope. 

What is rennet and how is it prepared? 

If the total solids of milk were reduced 5% by the addition of 
water how would it effect the percentages of each other constit- 
uent in the milk? 

What two agencies hasten the action of rennet on milk? 

How does pepsin compare with rennet in coagulating milk in 
cheese making? 



DAIBY LABORATORY EXERCISES 73 



74 DA1EY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 75 

COW TESTING ASSOCIATION EECOEDS 

One of the purposes of a cow testing association is to obtain the 
yearly production records, for milk and fat, of each cow in the as- 
sociation. In the usual proceedure about 25 producers form an 
association and employ a man for a year to weigh and test for fat, 
once each month, two successive milkings from each cow in each 
herd in the association. The monthly record for each cow is ob- 
tained by multiplying the production record for the day she is 
tested by the number of days in that month. From this data the 
yearly records are calculated. 



76 DAIRY LABORATORY EXERCISES 

EXERCISE XIV 

BABCOCK TEST, COW TESTING ASSOCIATION EXPEBIMENT 

1. Test for fat by the modified Babcock method a sample of ice 
cream and a sample of powdered milk. 

2. Cow testing association experiment. 

Go to a nearby dairy at milking time and obtain samples of 
milk from five cows on two successive milkings. The samples 
should be proportionate to the yield. Then the two from the same 
cow may be mixed and tested. Enough milk should be taken 
from each of the two messes so that when mixed together the 
amount will be large enough to permit the lactometer reading to be 
taken — approximately 200 cc. 

Record the weight of milk at each milking. Test the samples 
for fat by the Babcock method and take the lactometer reading. 

Then calculate the pounds of milk, pounds of fat and pounds of 
solids not fat each cow would produce in 30 days. 

3. Save, without preserving, a sample of milk for the next 
exercise. 

QUESTIONS 

What is a cow testing association? 
How is it operated? 

How do the tests of the milk made by the cow testing associa- 
tion compare with the test of that milk when it is sold at the 

factory? 

What are the duties of the tester who does cow testing associa- 
tion work? 

Why canont ice cream be tested for fat in the same way as 
ordinary cream? 

Why does the modified Babcock test for fat in ice cream give 
better results than the regular Babcock method as applied to test- 
ing ice cream? 

Briefly describe two methods of manufacturing milk powder 
and give difference in composition of the product by different 
methods. 



DAISY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



DAIET LABOEATOEY EXERCISES 



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DAIRY LABORATORY EXERCISES 



EXERCISE XV 

TESTING SOUR MILK, EFFECT OF TEMPERATURE, USE OF 
DIFFERENT ACIDS 

1. Test for fat the sample of coagulated milk soured from pre- 
vious exercise, first by measuring out the sample after thorough 
mixing; secondly by adding 1 gram of powdered sodium hydrate 
to dissolve casein, then testing as before. 

3. Effect of temperature on volume. Measure out at room 

temperature (about 70°F.) a sample of milk for Babcock test. 

Cool the milk to as near freezing as possible and measure out a 

Babcoek test. Heat the milk to 180°F. and measure out sample 

for Babcock test. Test the samples and compare the results. 

•"). Place 18 grams of milk into each of 5 Babcock milk test 
bottles — To No. 1. add 17.5 cc. of hot water. 

To No. 2. add 17.5 cc. of hydrochloric acid. 
To No. 3. add 17.5 cc. of glacial acetic acid. 
To No. 4. add 17.5 cc. of nitric acid. 
To No. 5. add 17.5 cc. of sulphuric acid. 
Proceed to complete the test as in the regular Babcock method. 

QUESTIONS 

1. What is the maximum limit of error allowed for a cream 
testing balance? 

2. When milk is heated why does a skin form on its surface? 

3. What effect do alkalis have upon the constituents of milk? 

4. How do the different acids, used in experiment 5 compare in 
their action toward milk and milk fat? 

5. Why does the temperature of the contents of a Babcock test 
bottle vary in different parts of the bottle when the test is 
completed? 



DAIRY LABORATORY EXERCISES 



82 DAI BY LABOBATOEY EXEECISES 



EXERCISES 

PART II 



8-1 DAIRY LABORATORY EXERCISES 



EXERCISE XVI 

VARIATIONS IN COMPOSITION OF MILK, ACID TEST, 
ADULTERATION. 

1. Obtain a sample of fore milk, middle milk and strippings 
and also a sample of the entire milking - . All these samples should 
be taken from the milk of one cow and at one milking time. 

Make a fat test and lactometer reading of each sample. 
Estimate the percentage of solids not fat and total solids in 
each sample. 

2. Test a sample of milk for acid using both the tenth-normal 
alkali solution, the Farrington alkali tablet solution and the 
alcohol test. 

P.. (a) Test for fat by the Babcock method a sample of whole 
milk and a sample of skimmed milk and take a lactometer reading 
of each. 

(b) To 300 cc. of the milk just tested add 100 cc. of the skim- 
med milk. Make a fat test of the mixture and take a lactometer 
reading. 

(c) Then add to the mixture of whole milk and skimmed milk 
100 cc. of water. Make a fat test of the mixture and take the 
lactometer reading. 

From the data secured in Experiment 3-a what would be the 
theoretical composition of the milk in Experiment 3-(b) and 3-(c) ? 

4. From the data secured in experiment one and three deter- 
mine (a) The percentage of fat removed by watering; (b) the 
percentage of fat removed by skimming. 

QUESTIONS 

Why do Ave have two necks on skimmilk test bottles? 

Why does milk turn sour and the casein coagulate? 

Why were so many different tests for fat in milk developed 
between 1888 and 1890? 

Name the tests brought out during this period. 

What is meant by the term "colostrum"? Give its average 
composition and specific gravity. 



. DAIEF LABORATORY EXERCISES 85 

Why does milk from different parts of the udder vary in 
composition? 

What are the most common causes of the variation of the fat 
content of milk? 

What is the reason for the variation of the fat content of milk 
as drawn from the udder during a single milking? 



DAISY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 87 



DAIRY LABORATORY EXERCISES 



EXERCISE XVII 



COMPARING DIFFERENT FAT TESTS, EFFECT OF TEMPERATURE 
AND TESTING MILK POWDER 

1. (a) Using Professor Feser's Lactoscope, determine the per 
cent of fat in a sample of milk and compare with the Babcock 
method. 

(b) Using- Heren's Pioscope, compare the samples furnished in 
respect to per cent of fat. Check your results by the Babcock 
method. Draw conclusions. 

2. Test a sample of cream with a 9 gram, 6 inch cream bottle 
and with a 9 gram, 9 inch cream bottle. Place the completed 
test in a water bath and raise the temperature of the water from 
100° F. to 180° F. Take readings at every 10 degrees rise in 
temperature. Do not use meniscus remover in this experiment. 
For comparison read from bottom of fat column to bottom of top 
meniscus. Draw conclusions as to effect of temperature on 
volume of the fat. 

3. Weigh into a milk test bottle 2.5 grams of milk powder. 
Add 15.5 cc. of warm water, dissolve by shaking, cool and test 
for fat as for whole milk. Calculate the per cent of fat. 

QUESTIONS 

By whom was the Pioscope invented? 

Who invented the Lactoscope? 

Upon what physical properties of the milk are these tests based? 

What was the cream gauge method of determining the per cent 
of fat in milk ? How was the per cent of fat determined by this 
test? 

If the graduated portion of a 9 gr. cream test bottle was full 
of butter fat, what would be the w r eight of the fat? 

Give a brief history of the development of milk fat tests. 

If seven grams of 30% cream were placed in a 9 gram cream 
test bottle what would be the volume of fat in cc. in the neck 
of the bottle and what would the percentage reading on the scale 
be when the test is completed ? 



DAISY LABORATORY EXERCISES 



DAIRY LABORATORY EFERCISHS 



DAIRY LABORATORY EXERCISES 91 

EXERCISE XVIII 
THE BABCOOK AND SHAW BUTTER FAT TESTS 

1. Test butter for per cent of fat by the Babcock method using 
different kinds of butter bottles and cream test bottles. 

2. Test the butter by the Shaw method and compare the re- 
sults with the Babcock method where different kinds of bottles 
were used. 

The Shaw Method : Clean, dry and weigh the special sep- 
aratory funnels. Weigh into a 100 cc. glass beaker, after bal" 
ancing it on a scales, 20 grams of the properly mixed sample. 
Warm the beaker or add a little hot water to melt the butter. 
Pour it into the separatory funnels. By repeated washings with 
a fine stream of hot water using not more than a teaspoonful 
each time, rinse the beaker free from fat until the funnel is full 
to within one-quarter of an inch of the shoulder. Using the 
special socket centrifuge the funnels. The socket must be placed 
in the centrifuge with the open side facing the direction in which 
the disc revolves. The centrifuge must be warm. Whirl one 
minute at speed used for milk. Remove the funnels and draw 
off the water (using care not to permit the cocks to stick) until 
the casein is within one-eighth of an inch of the stopcock. Then 
add 9 cc. of cold water and 11 cc. of Babcock sulphuric acid after 
mixing them together in a beaker. Mix to dissolve the curd, 
centrifuge as before. Draw off the acid solution until the fat is 
within one-fourth of an inch of the stopcock, and repeat the 
addition of the acid, once more. After drawing off the second 
acid solution, centrifuge another minute and allow the fat to 
come down through the stopcock to the end of the capillary stem. 
Carefully dry the separatory funnels on the outside with a clean 
towel and weigh. The weight thus obtained minus the weight 
of the funnels equals the weight of butter fat in 20 grams of the 
butter. One addition of the acid may suffice, but usually two 
additions are necessary. If the weight of the clean dry funnels is 
once secured, it will not be necessary to have them dry on the 
inside before using. If any glass is chipped off they should be 
reweighed. 



DAISY LABORATORY EXERCISES 



QUESTIONS 

Why will variations in the specific gravity of the butter fat 
make the Babcock test less accurate than the Shaw test for fat 
in butter? 

Why may not the regular cream test bottle be used for testing 
butter for fat? 

Name four sources of error that are difficult to avoid in making 
the Shaw Butter fat test. 



DAI FY LABORATORY EXERCISES 93 



94 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 95 



EXEKCISE XIX 

COMPARISON OF THE BABCOCK AND ADAMS TESTS FOR FAT 
IN MILK 

1. Test in duplicate a sample of whole milk and skimmed milk 
for per cent of butter-fat by the Babcock method and compare 
the results with those obtained by the following chemical method. 

2. Adams Methods : For this method, a strip of fat-free filter 
paper 2% inches wide and 22 inches long is rolled into a coil and 
held in place by a wire about 8 inches in length, wound once 
around the coil and projecting one end of the wire for use in 
hanging the coil up for drying. About 5 grams of milk is meas- 
ured into a small beaker with a pipette, and the weight of the 
beaker and milk taken. One end of the coil is then intro- 
duced into the beaker in such a manner that as much as 
possible of the milk is absorbed by the paper. By then weighing 
the beaker, the amount of milk absorbed by the paper coil is 
determined by the difference, and the paper coil hung up and 
dried, first in the air, and then in the water oven at a temperature 
not exceeding 100° C. The coil containing the dried residue is 
then transferred to the Soxhlet extraction apparatus and sub- 
jected to continuous extraction with anhydrous ether for at least 
two hours, the receiving flask being first accurately weighed. The 
tared flask with its contents is freed from all remaining ether 
first on the water bath and finally inj the air oven. The flask is 
then cooled in the dessicator and weighed; the increase in weight 
represents the amount of fat in the milk absorbed by the paper 
coil. Two hours is usually sufficient for the extraction of the fat, 
when the conditions are such that the ether siphons over from 
the extraction tube ten times per hour. 

Tabulate the results of this experiment. 

Make a drawing of the Soxhlet fat extraction apparatus as set 
up for the Adams method. 

3. Sediment Test : Determine the amount of sediment in the 
different grades of milk by means of a Wizard sediment tester. 
Dry the different sediment pads on a clean sheet of paper that is 
to be handed in with report. 



96 DAIRY LABORATORY EXERCISES 



QUESTIONS 



In the Adams test for fat in milk why must the coil containing' 
the milk be dried before extracting with ether. 

How do the Adams, Mojonnier, and Babcock methods agree in 
determining the fat content of skimmed milk. 

Does the prolonged heating of the fat in the water oven when 
driving off the last traces of ether affect the percentage of fat 
in any way? If so why? 

What precautions are necessary in determining the amount of 
milk that is transferred to the paper coil in the Adams fat ex- 
traction method? 



DAIRY LABORATORY EXERCISES 97 



DAIRY LABORATORY EXERCISES 



DAISY LABOBATOBY EXEECISES 



EXERCISE XX 



COMPOSITION OF BUTTEE BY THE GEAVIMETEIC AND KOHLMAN 
METHODS 

1. The chemical gravimetric method for 'butter moisture : Pre- 
pare a sample of butter for the moisture test. "Weigh out in tared 
dishes between 2 and 3 grams of the butter and evaporate at the 
temperature of boiling water for 10 hours. Cool in dessicator 
and weigh. The loss in weight divided by the weight of butter 
equals the per cent of water in the butter. 

2. Test a 10 gram sample of the butter for moisture using a 
tall aluminum beaker on an asbestos pad over a gas flame for 
driving off the water and compare the results with those found 
hy the chemical gravimetric method. 

3. After cooling and weighing the beaker to determine loss of 
moisture in problem 2, fill it with petroleum ether and stir the con- 
tents with a glass rod. Cover and let stand about three minutes for 
solids to settle. Decant off the clear solution. Repeat the wash- 
ing with the petroleum ether and decant off as before. Gently 
heat the beaker to remove last traces of petroleum ether. Heat 
carefully to avoid sputtering. 

Reweigh the beaker and contents and determine the percentage 
of fat dissolved off. 

Dissolve the contents of the beaker in 300 cc. of warm water 
and determine the percentage of salt in the butter by the Cornell 
Method. 

QUESTIONS 

1. What is the disadvantage to a creameryman of the chemi- 
cal gravimetric method for determining moisture in butter? 

2. Why is petroleum ether used in the Koleman method for 
estimating the fat content of butter? 

3. What substances remain in the beaker after the moisture, 
fat and petroleum ether have been driven off? 

4. How is the per cent of curd determined? 



DAISY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 101 



102 DAISY LABORATORY EXERCISES 

THE MOJONNIER TEST FOR FAT AND SOLIDS IN MILK AND ITS 
PRODUCTS 

The Mojonnier tester and methods of analysis enables a chemist 
to determine the percentages of fat and solids in milk and all 
products made from milk, quickly and with a high degree of 
chemical accuracy. It modifies and adapts to factory conditions 
the Roese-Gottleib wet extraction method for fat determinations 
so that, in place of requiring several hours, tests may be com- 
pleted in less than thirty minutes and the solids test may be 
run along with the fat test and completed in a short time. This 
enables the manufacturer of concentrated dairy products to learn 
the exact composition of his raw materials so quickly that he ran 
control the composition of his finished product to meet the most 
exacting state, federal and quality standards. 

The principal apparatus used in the Mojonnier method is the 
tester. It compactly combines electric hot plates, vacuum drying 
ovens, cooling ovens, centrifuge, power unit and chainomatic 
chemical balance. Special extraction flasks, evaporating dishes 
and pipettes are also provided. 



DAIRY LABORATORY EXERCISES 103 



EXERCIESES XXI— XXII 

THE MOJONNIER TEST FOR MILK FAT AND SOLIDS 

1. Make a study of the parts and the mechanism of the 
Mojonnier tester. 

2. Learn how to manipulate the Mojonnier fat and solids test 
and the reasons for using each reagent in the fat test. 

3. Test a sample of whole milk for fat and solids by the 
Mojonnier method. 

4. Take the lactometer reading of the whole milk tested under 
(3) and make a Babcock test of it. Calculate the percentage of 
total solids by applying formulas. 

5. Compare the percentages of fat and the total solids ob- 
tained by the two methods. 



104 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 105 



106 DAIRY LABORATORY EXERCISES 



EXERCISES XXIII— XXIV 

TESTING AND STANDARDIZING BEFORE CONDENSING A BATCH 
FOR THE .MANUFACTURE OF EVAPORATED MILK * 

1. Test the milk, skim-milk and cream on hand for fat and 
solids, using the Mojonnier method. 

2. Calculate the number of grams of skim-milk or cream that 
must be added to 1000 grams of the milk to bring its percentage 
of fat and solids not fat to the desired ratio. 

3. Add to 1000 grams of the milk the amount of skim-milk or 
cream required as found under (2) and test the mixture for fat 
and solids by the Mojonnier method. 

4. After testing the mixture calculate its ratio of fat to solids 
not fat and compare the result obtained with the desired ratio. 



* Note : Methods for solving standardizing problems are given in the 
book The Technical Control of Milk Products by Mojonnier and Troy 1922. 



DAIRY LABORATORY EXERCISES 107 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



EXERCISES XXV— XXVI 



TESTING AND STANDARDIZING BEFOBE CONDENSING A BATCH 
FOB THE MANIJFACTUBE OF SWEETENED CONDENSED MILK 

1. Test the milk, skim-milk and cream on hand for fat and 
solids using the Mojonnier tester. 

2. Calculate the number of grams of skim-milk or cream that 
must be added to 1000 grams of the milk to bring its percentage 
of fat and solids not fat to the desired ratio. 

3. Make up the mixture as calculated under (2) and calculate 
the grams of sugar to add to obtain the desired composition. 

4. Make up the mixture as calculated and test it for fat and 
solids using the Mojonnier method. 

Calculate the ratio of fat to solids not fat obtained. 
Calculate the ratio of fat to total solids obtained. 



DAISY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 111 



112 DAIRY LABORATORY EXERCISES 

EXERCISES XXVII— XXVIII 

TESTING AND STANDARDIZING ICE CREAM MIX 

1. Make up a 1000 gram batch of ice cream mix so that the 
fat is about 0.3 per cent under, and milk solids not fat about 
0.5 per cent over the desired standard. (See ff3 for desired 
standard.) 

2. Determine by using - the Mojonnier method the exact per- 
centages of fat and milk solids not fat in the mix. Also make 
these tests on the cream to be used in standardizing the mix. 

3. Calculate the grams of cream, sugar and water that must 
be added to the mix in order to make it test 10% of fat, 11% of 
milk solids not fat and 13% of sugar. 

4. Add the standardizing materials to the 1000 gram batch, 
mix thoroughly and test by the Mojonnier method for fat and 
solids. 

Compare the percentages of fat and milk solids not fat obtained 
with those desired. 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 115 



EXERCISES XXIX— XXX 
TESTING AND STANDARDIZING ICE CREAM MIX (CONTINUED) 

1. 'Make up a 1000 gram batch of ice cream mix so that the 
fat is about 0.5% over the percentage finally desired and the milk 
solids not fat about 0.3% under the percentage finally desired. 

2. Determine by the Mojonnier method the exact percentages 
of fat and milk solids not fat in the mix. Also make these tests 
on the condensed skim-milk to be used in standardizing the mix. 

3. Calculate the grams of condensed skim-milk, sugar and 
water that must be added to the mix in order to make it test 10% 
of fat, 11% of milk solids not fat and 13% of sugar. 

4. After adding the necessary standardizing materials mix the 
batch thoroughly and make certain that the sugars are in solu- 
tion. Again test the mix for its percentages of fat and milk 
solids not fat and compare the results with the composition 
desired. 



116 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



118 DAIRY LABORATORY EXERCISES 



EXERCISES XXXI— XXXII 

TESTING AND STANDARDIZING ICE CREAM MIX (CONTINUED) 

1. Make up a 1000 gram batch of ice cream mix so that the 
percentages of fat and milk solids not fat present are both about 
.5 per cent under that desired. 

2. Test the batch for fat and milk solids not fat by the 
Mojonnier method. Also test the materials that are to be used in 
standardizing the batch. 

3. Calculate the grams of each material to add to bring the 
fat and milk solids not fat up to the desired percentages. 

4. Add the materials to the original mix and test the mix for 
fat and milk solids not fat by the Mojonnier method. Compare 
the percentages obtained with the percentages- desired. 



DAIRY LABORATORY EXERCISES 119 



12 o DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 121 



EXERCISES XXXIII— XXXIV 

MAKING AND CHECKING STANDARD ACID AND ALKALI . 
SOLUTIONS. 

1. Make up an alkaline tablet solution by dissolving 26 Far- 
rington alkaline tablets in small amount of distilled water and 
make the solution up to 100 cc. Determine the strength of alka- 
line solution by titrating with a standard HC1 solution. What 
weight in grams of NaOH does each tablet contain? How many 
grams of lactic acid does each tablet neutralize according to your 
results 1 

2. Cork a clean dry test tube and weigh it accurately on a 
chemical balance. Working quickly, place in the weighed tube 
a stick of C. P. NaOH between two and three inches long. Cork 
the tube at once and reweigh. Determine the weight of caustic 
in the tube and dissolve it in distilled water at the rate of .416 
grams for each 100 cc. of solution. Determine the strength of 
N/10 NaOH solution by titrating it against standard tenth normal 
hydrochloric acid and tenth normal oxalic acid solution. The 
standard HC1 solution will be furnished. To prepare tenth nor- 
mal oxalic a*cid (C 2 H 2 4 -f 2H 2 0) dissolve in distilled water at 
the rate of .63 grams for each 100 cc. of solution. 

3. Test a sample of skimmed milk for per cent of acid by 
using each alkaline solution. Save some of the milk to be tested 
for acid at the next laboratory period. 

4. Test a sample of vinegar for per cent of acid by using each 
alkaline solution. 

Molecular formula for acetic acid = CH 3 COOH 

It will be necessary to determine the specific gravity of the 
vinegar. This may be done with a Quevenne lactometer. 

5. Slake a few ounces of lime in a small amount of warm 
water. Add about 100 cc. of water to the slaked lime, and set 
aside until the next exercise. 

6. Place 300 cc. of concentrated HC1 in an evaporating dish. 
Add 200 cc. of water. Boil down to 200 cc. or y 2 of the original 
volume. The specific gravity then equals 1.10. It contains 20.2% 



122 DAISY LABORATORY EXERCISES 

HC1. IS grams of this solution diluted to 1000 ce. gives an N/10 
solution of HC1. (18.0 X 20.2% = 3.636 grs.) 
Using the above method make up an N/10 solution of HC1. 
Note : Aliquot portions of the above amount may be used. 

QUESTIONS 

What is the advantage in using Farrington alkaline tablets in 
making an alkali solution? 

Give the grams per cc. in tenth normal solutions of (a) three 
acid solutions; (b) three alkali solutions; (c) three salt solutions. 

How much NaOH by weight does each tablet contain? 

What is the legal requirement for vinegar in New York state? 

What is the normality of a limewater solution? 

If a N/10 KOH solution and a N/10 NaOH solution were mixed 
together, how would you use the resultant solution in determining 
the acidity in a sample of milk? 

How does the specific gravity of vinegar vary from that of 
milk? 



DAISY, LABORATORY EXERCISES 123 



DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 



EXERCISES XXXV— XXXVI 



MILK ANALYSIS, AND MODIFIED LEEFMAN-BEAM METHOD FOE 
FAT IN MILK AND CREAM. 

1. Milk analysis. Take the Sp.Gr. of a sample of milk with. 
Quevenne lactometer, and measure three cc. of the milk into a 
weighed silica dish. Evaporate to a constant weight at the 
temperature of boiling water (100° C). Cool in a dessicator 
and weigh. Determine the per cent of fat by the Babcock 
method. Compare the per cent of solids obtained by the gravi- 
metric method, with the per cent of solids calculated by applying 
different formulas. 

2. Heat the silica dish containing the residue from No. 1 in 
the muffle to an ash. Cool in the dessicator, reweigh, and deter- 
mine the per cent of ash in the milk. 

What conclusions do you draw in No. I? 

1. Test in duplicate a sample of milk and cream for per cent 
of buter fat by the Babcock 'method. If the fat column in the 
completed test is not a clear, straw color, with sharply denned 
lines, the test must be repeated. Compare the results of this 
method with the results you obtained by the following modifica- 
tion of the Leffman-Beam method. 

2. MODIFIED LEFFMAN-BEAM METHOD: 

Test for per cent of fat in Milk : Prepare the sample of milk 
and measure the charge by following the Babcock method up 
to the point of adding sulphuric acid. Then proceed as follows : 

1. Add 3 cc. of a mixture of Amyl alcohol and Hydrochloric 
acid (equal parte of Amyl alcohol and Hydrochloric acid). 

2. Add 12 cc. of Sulphuric acid cautiously, mix and let stand 
for 3 minutes or until all the protein is dissolved and fat has 
risen to the top. 

3. Add to top of graduation on neck of bottle a mixture of 
hot and freshly made solution of equal parts of sulphuric acid 
and water. NOTE : In making the solution, add the acid to the 
water. 

4. Whirl in centrifuge at the usual speed of Babcock test 
for 5 minutes. 



126 DAIRY LABORATORY EXERCISES 

Reading the Test : Make three readings of the fat column. 

1. From bottom of fat column to bottom of top meniscus. 

2. From bottom of fat column to middle of top meniscus. 

3. From bottom of fat column to top of meniscus. 
Record all results. 

Test for per cent of fat in Cream : Prepare the sample of cream 
same as for Babcock test, and weigh 9 grams of the sample into a 
9-gram cream test bottle, adding 9 cc. of water. Complete the 
test by following the method given for milk with the exception 
of adding a little less sulphuric acid. 

Reading the Test: Temper the cream test in water bath at a 
temperature of 130°— 140° F. for 3 to 5 minutes. Make the fol- 
lowing readings and record each: 

1. Bottom of fat column to bottom of top meniscus. 

2. Bottom of fat column to middle of top meniscus. 

3. Bottom of fat column to top of meniscus. 

4. Add meniscus remover and read from bottom of fat column 
to the sharp line at the junction of meniscus remover and fat 
ci lumn. 

The official chemical results of this experiment will be given 
out at the close of the laboratory period. 

Enumerate and describe the desirable and undesirable features 
of each method in this exercise. Include^ a tabulated form of all 
results. 

QUESTIONS 

1. How do the percentages of solids not fat and total solids 
of milk as determined by the chemical method compare with 
those obtained by the use of the different formulae? 

2. Why should ash determinations be made in a muffle? 

3. What is the purpose of adding the mixture of amyl alcohol 
and hydrochloric acid in the Leffman-Beam method of testing 
milk for fat? 

4. How does this test compare with the regular Babcock test? 



DAISY LABOEATOSY EXERCISES 127 



128 DAIRY LABORATORY EXERCISES 



DAIRY LABORATORY EXERCISES 129 



EXERCISE XXXVII 

HART AND WALKER CASEIN TESTIS, GERBER FAT TEST, 
DETERMINING THE SOLUBILITY OF CASEIN. 

1. Walker Casein Test. Titrate 9 c c. of sweet milk in 
a white cup for per cent of acid using N/10 alkali solution. Use 
1 c. c. of a 1% phenolphthalein solution as indicator. Stir con- 
stantly with a glass rod during the titration, and titrate to a fair- 
ly deep pink color. Then add 2 c. c. of neutral 40% formalde- 
hj'de solution. Take the reading on the burette and again run in, 
with constant stirring, the alkaline solution until the same degree 
of pink color again developes. The number of cc. of tenth nor- 
mal solution used for the final titration multiplied by 1.63 gives 
the per cent of casein in the milk. Set aside some of the milk un- 
til the next exercise and again test it to determine if one may use 
this test for the per cent of casein in sour milk. 

2. Test a sample of milk for fat by the Gerber method and 
compare the results with a test made by the Babcock method. 

3. The Hart Casein Test : Place 2 c c. of chloroform in 
the casein test tube, add 20 c. c. of a 0.25% solution of acetic acid 
at a temperature of 65 to 75° F. (10 cc. of glacial acetic acid dilut- 
ed to 100 with water then diluting 25cc. of this solution to lOOOcc.) 
5 cc. of milk at a temperature of 65 to 75 °F is then run in, the tube 
covered with the thumb and inverted and the mixture shaken vig- 
orously for exactly 20 seconds, centrifuge within 20 minutes at a 
speed of 2000 revolutions per minute. Allow to stand ten minutes 
before reading the per cent of casein. Cheek the results by the 
"Walker method. 



130 DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 131 



132 DAIRY LABORATORY EXERCISES 



EXERCISE XXXVIII 

4. TESTING CASEIN FOR SOLUBILITY AND ADHESIVE 

PROPERTIES 

4. Dahlberg Method : Place 50 grams of the powdered casein in 
a flask, beaker or dish, add about 100 cc. of water, measuring the 
amount. Mix the water and casein thoroughly. In another vessel 
place 5 grams of borax and add 75 cc. of water to it. Heat the wat- 
er and mix until borax is dissolved. Pour the borax soultion on the 
casein mixture and add water to bring the volume of the mixture 
('. for quite a long time (30 to 60 minutes) with stirring until all 
casein is in complete solution. (Sometimes 2 c. c. of concentrated 
NH 3 are added to the mixture to assist solution but it is not usual- 
ly added.) Then take 100 grams of Kaolin, (china clay) add 60- 
70 c. c. of water and work to a smooth heavy paste. To all of this 
Kaloin mixture add 30 gramd of the casein mixture (6 grams of 
the casein) and thoroughly mix by use of a large spoon or similar 
instrument in a 3 pint bowl until the paste is very smooth. May 
also use brush in mixing. Then by using the brush transfer some 
of the mixture to a piece of brass, spreading it along a straight 
edge. Then spread the mixture without delay evenly on paper 
by holding the brass in a slanting position and pressing the mix- 
ture into the paper. The brass should be drawn across the paper 
with a quick motion. To the portion of the Kaolin-casein-borax 
mixture that remains add 5 grams more of the casein-borax mix- 
ture, mix it thoroughly and spread on paper as before. 

Then make one more mixture by adding 5 more grams of 
the casein-borax-water solution and again spread on paper and 
let dry. 

Test each mixture for adhesive properties by heating the end 
of a rod of wax till soft, then sticking it on the paper. 

When cool pull the wax off. The mixture which gives the 
best results is the proportions that should be used in making the 
sizing. The best results are indicated by the amount <>f paper 
that sticks to the wax and fiber that is pulled up from the paper. 
The wax should be pulled off perpendicular to the paper. And 
the more shreds of paper and solid paper substances that sticks to 
the wax the better the quality of the casein. 



DAISY LABORATOBY EXERCISES 



QUESTIONS 

For Walker Casein Test, read article in Journal of Industrial 
& Engineering Chemistry, Feb. 1914, p. 131. 

Make a drawing of the Gerber milk test bottle. 

What is your opinion of Gerber method as compared with 
Babcock method? 

Explain why the per cent of fat may be read directly in the 
Gerber milk test bottle. 

What is the purpose of the different reagents used in the 
Hart Casein test ? 

Why is borax used in the Casein Solubility test? 



DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 135 



136 DAIRY LABORATORY EXERCISES 

EXERCISE XXXIX 

DETECTING BUTTER SUBSTITUTES 

1. Melt samples of the butter substitutes in large test tubes 
two-thirds full. Keep at a temperature of about 150°F, until well 
melted and most of the casein and water have separated. Note 
any differences in transparency of the melted fat, when compared 
with the melted fat from pure butter. 

2. Over a flame about an inch high from an alcohol lamp, gas 
jet, or kerosene lamp, heat in a teaspoon a quantity of the sub- 
stance about the size of a chestnut. Heat slowly until melted, 
then rapidly until the water is nearly boiled off. Note any differ- 
ences in the amount of foam formed and the length of time elaps- 
ing before the bubbles of foam break, when compared with pure 
butter heated in the same manner. 

3. Fill a pint tin cup half full of skimmed milk, and heat near- 
ly to boiling. Place a piece of the sample about the size of a 
butternut in the hot milk. Set the cup in a pan of ice water, and 
stir briskly by a rotary motion with a small wooden splinter a 
little longer than a match in diameter. When the fat begins to 
harden, it may readily be gathered into a mass at the center or in 
a lump on the end of the splinter if it is oleo. Butter fat or ren- 
ovated butter will not gather so readily, but will float on the 
surface spread out quite uniformly. 

4. Halpen's Test for Cotton-Seed Oil: To 3 cc. of the oil or 
melted and filtered fat in a small test tube, add 3 c. c. of amyl al- 
cohol and 3 c. c. of a one per cent solution of sulphur in carbon 
disulphide. Heat the test tube in a boiling salt saturated water 
solution for 10 or fifteen minutes. If cottonseed oil is present, the 
mixture turns red. 



DAIRY LABORATORY EXERCISES 137 



138 DAIRY LABORATOBY EXEBCISES 



DAISY LABORATORY EXERCISES 



EXERCISES XL— XLI 

REICHERT-MEISSL NUMBER OF BUTTER AND OLEOMARGARINE, 
AND MAKING VISCOGEN 

1. Melt about 30 grams of the substance in a test tube, at a 
temperature of about 140 °F. and hold at this temperature until 
the water and casein have separated. Filter the liquid fat 
through a dry filter with funnel inserted into a convenient Erlen- 
lneyer flask; keep warm in the 100°C. oven to assist the Alteration 
process. Measure 5.75 c. c. of the filtered fat into a weighed 300 
c. c. Erlenmeyer flask that has been thoroly cleaned and dried 
in the water oven. Cool and weigh to get the amount of fat 
raken; saponify the fat adding 20 c. c. of a soda glycerine solution 
(20 c. c. of 50% solution of sodium hydroxide in 180 c. c. of glyc- 
erine), heating the flask in the 100°C. oven, or over a bunsen 
flame. The solution is perfectly clear when saponification is com- 
plete. Then add 135 c. c. of water, drop by drop at first, to pre- 
vent foaming. A pinch of pumice stone powder is added, and 5 c. 
c. of dilute sulphuric acid solution (20 c.c. of Cone. H 2 S0 4 -+- 
80 c.c. of distilled water.) Connect the flask to the condenser, 
using distilling connecting bulb, and distill over 110 c. c. of the 
volatile fatty acids. Mix the distillate, and if not perfectly clear, 
filter. Titrate 100 c.c. of the distillate with N/10 NaOH, using 
phenolphthalein as indicator, and increase the number of c. c. of 
N/10 NaOH required, by one-tenth to obtain the Reichert-Meissl 
number. 

2. Viscogen: Slake one ounce (28.35 gr.) of quick lime in 
sufficient hot water to nearly cover it, using a pint milk sample 
bottle. Mix during the slaking process. The substance should 
be in a pasty condition when slaked. Add 150 c. c. of cold water. 
Dissolve 3 oz. of sugar in 150 cc. of water, and mix it thoroughly 
with the slaked lime solution. Mix at intervals for a few hours*, 
Let settle and use the clear solution at the next exercise. 

Note : Viscogen may be made in large quantities for com- 
mercial purposes by slaking 3 pounds of good quick lime in water. 
Make the volume up to 5 gallons by adding water. Dissolve 10 
lbs. of sugar in 5 gallons of water. Mix the two solutions and stir 
at intervals for 3 hours. Let settle and use the clear solution. 



140 DAISY LABORATORY EXERCISES 

3. Determine the alkalinity of the viscogen made in 3. 
Make an acid test of a sample of cream and add a sufficient 
amount of viscogen to 25 cc. of the cream to just neutralize the 
acid. Determine the viscosity of the visco-cream and the original 
cream by comparing the distance that drops of equal size from 
each will flow on an inclined glass plate. 

QUESTIONS 

1. Make a drawing of the distilling apparatus used in determ- 
ining the Reichert-Meissl number. 

2. Give the variations and average Reichert-Meissl number 
and refractive index of butter and oleomargarine. 

3. What is viscogen and for what is it used? 



DAI BY LABOBATOBT EXERCISES 141 



142 DAISY LABOBATORT EXERCISES 



DAIRY LABOEATOEl EXEECISES 143 

EXERCISES XLII— XLIII 

MODIFYING MILK FOE INFANTS AND INVALIDS 

Cream, skini-niilk, milk sugar and water are mixed to obtain 
the desired percentages. 

Factors used in formulas : 
A = the percentage of fat in the cream 
B = the percentage of proteids in the skim-milk 
C = the ounces of cream required 
D = the ounces of sugar required 
E = the percentage of sugar in the cream 
F = the desired percentage af fat 
M = the ounces of skim-milk required 
N = the percentage of sugar in the skim-milk 
P = the desired percentage of proteids 
Q = the ounces of modified milk desired 
*R = the percentage of proteids in the cream 
S = the desired percentage of sugar 
W = the ounces of water required 

Problem : Make up 24 ounces of modified milk contain- 
ing 3.5% fat 1.25% proteids and 5.% milk sugar. 
Materials available for use : 

Cream containing 18% fat, 3.0% proteids, 4.0% sugar 
Skim-milk " 3.5% " 5.0% 

Milk sugar, 100% lactose 
Calculating the ounces of cream required : 

(FxQ) 

L ~ A 

Calculating the ounces of skim-milk required : 

„ (Q X P) - (C X K) 
M g 

Calculating the ounces of milk sugar required: 
D=(QXS) - [(CXC) + (MXN)] 
Calculating the ounces of water required : 
W = Q— (C + M-4-D) 
In addition to the problem given above another will be 



144 DAIRY LABORATORY EXERCISES 

given to each student. The mixtures are to be made up and test- 
ed for fat and total solids on the Mojonnier tester. 

QUESTIONS 

1. What is modified milk and for what purpose is it generally 
used ? 

2. What are three general methods of modifying milk? 

3. How is the percentage of each solid not fat in cream affect- 
ed by an increase in the percentage of fat .' 

4. If a sample of whole milk contained 4% of fat and 3.7% of 
protein, what percentage of protein would be found in cream con- 
taining 40</r of fat made by separating the milk! 



DAISY LABORATORY EXERCISES 



146 DAISY LAB0RA10EY EXERCISES 



DAIRY LABORATORY EXERCISES 147 

EXERCISES XLIV— XLV 
METHOD OF TESTING UNSWEETENED EYAPOEATED MILK: 

The sample is mixed by shaking, pouring and stirring. Exam- 
ine the surface closely and if fat particles are observed, warm 
the mixture to 100 °F. and again mix. 

Fat Test : Weigh 9 grams of the sample mixed as above into 
a Babcock milk test bottle. Add 9 c.c. of water and shake to mix 
thoroughly. Add about 17.5 c. c. of sulphuric acid. Mix thor- 
oughly, then add about 2 c. c. more of the acid, and shake vigor- 
ously for two or three minutes. Complete the test as for whole 
milk. The fat reading multiplied by 2 gives the per cent of fat. 

METHOD OF TESTING SWEETENED CONDENSED MILK FOE 
PEE CENT OF FAT. 

Mix thoroughly by transferring the contents of the can into a 
convenient dish and stirring until homogeneous. Weigh out 40 
grams and wash it into a 100 c. c. flask and make up to the mark 
with water, or the 40 grams may be weighed directly into the 
flask before making up to the 100 c. c. mark. 

Place 15 c. c. of this 40% solution in a Babcock milk test bottle. 
Fill the bottle nearly to the neck with water, add 4 c. c. of Feed- 
ing's solution, shake thoroughly and rapidly, centrifuge, pre- 
ferably in a cold machine. The casein and fat are thrown to the 
bottom. Withdraw the supernatant liquid by means of small- 
stemmed pipette with a wisp of wet absorbent cotton twisted over 
the tip to serve as a filter. Wipe off the cotton into the bottle on 
withdrawing the pipette. Give the precipitated proteids and fat 
two additional washings by shaking up with water, again centri- 
fuging and removing the water each time with the pipette. If the 
precipitate is caked hard after centrifuging, it must be broken 
up hy using a fine wire stirrer. Finally, add water to an approxi- 
mate volume of 17.5 cc. and add 17.5 cc. of Babcock sulphuric acid 
and complete the test as for milk. The reading multiplied by 
3 gives the per cent of fat in the sample. 

Note: Fehling's copper solution = 34.639 grams of pure 
copper sulphate (CuS04 . 5H 2 0) dissolved in water and diluted 
to exactlj* 500 c.c. 



148 DAISY LABOBATOBI EXEBCISES 



DAIRY LABORATORY EXERCISES 149 



150 VAIRT LABORATORY EXERCISES 

TESTING ICE CREAM FOE BUTTER FAT: METHOD BY 
A. W. RUDNICK. 

Weigh out 9 grams of the freshly melted and mixed sample in 
a 9-gram, 6-inch, 50% cream test bottle. Add 9 c. c. of dilute sul- 
phuric acid (1 of acid to 3 of water) saturated with ammonium 
sulphate, and centrifuge for 5 minutes at a little higher speed 
than for ordinary testing. Pour off or draw off the liquid by 
means of a pipette. Add 9 c. c. of water and proceed as in the 
cream test. 

If nuts or fruit have been used, these should be ground very 
fine, preferably by means of a mortar and pestle, and the fat col- 
umn brought into the neek by using denatured alcohol instead of 
water. Read the fat column in this case from the extreme bottom 
to the extreme top. 

.METHOD OF PROF. H. E. ROSS FOR TESTING ICE CREAM 

Mix equal parts by weight of the melted ice cream and water. 
The water should be at a temperature of about 100°F. and the 
mixing is best done by pouring the mixture from one vessel to an- 
other. Weigh into a cream bottle 9 grams of the mixture. A 9- 
gram cream bottle with a body the size of an 18-gram cream bottle 
is best, although a regular 18-gram cream bottle may be used. To 
the 9 grams of the mixture add 17.5 c. c. of the glacial acetic acid. 
Thoroughly mix the acid and cream by shaking the bottle from 
two to three minutes. Next add 15 cc. of sulphuric acid such as 
is commonly used for the Babcock test. Thoroughly mix the con- 
tents of the bottle by shaking about a minute. Then proceed 
with the test in the ordinary way. If a 9-gram bottle is used, the 
result should be multiplied by 2 as the cream was diluted one-half. 
If an 18-gram cream bottle was used, the result should be multi- 
plied by four, as the cream was diluted one-half and one-half the 
regular amount was used for the test. 

METHOD OF J. P. DAWSON FOR TESTING ICE CREAM 

Weigh 18 grams of melted ice cream at a temperature of 70 °F. 
into a 30%, 9-inch cream test bottle. Add 8 c. c. of glacial acetic 
acid, agitate gently for 2 minutes, and add 10 c. c. of sulphuric 



DAIRY- LABORATORY EXERCISES 151 

acid. Shake thoroughly and centrifuge and complete the test in 
the usual manner for ordinary cream. 

Note : There appears to be no reason why the above described 
method would not work equally well using 9 grams of the ice 
cream and an 8-inch 50% 9-gram cream test bottle, and adding 
onlv one-half the volume of acids. 



152 DAIRY LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 



DAIRY LA BO B A TOBY EXESCISES 



EXERCISES XLVI— XLVII 

TESTS FOR PRESERVATIVES AND ADULTERANTS, 
TESTS FOR BOILED MILK 

To 10 or 15 ee. of milk in a test tube or bottle add an amount 
of calcium peroxide the size of a kernel of wheat, shake and add 
the same amount of paraphenylenediamine-hydrochloride. Again 
shake the mixture and if the milk was not boiled or heated above 
175 °F. it will develop a blue color in a few minutes. 

SECOND TEST FOR BOILED MILK 

Add one c.e. of a slightly pasty starch solution that was 
made by boiling starch in water, to 10 or 15 cc. of milk in a test 
tube or bottle, next add 5 to 6 drops of a 10% solution of potassium 
iodide and finally a pinch of calcium peroxide the size of a kernel 
of wheat and shake. A blue color will develope in a few minutes 
if the milk has not been heated above 175 °F. 

TEST FOR MYSTIN (A COMPOUND OR MIXTURE OF FORMALDE- 
HYDE AND A NITRITE.) 

Five cc. of milk or cream are mixed with 5 cc. of water and 
to it are added 0.5 cc. of a 10% solution of urea, then 1 cc. of nor- 
mal (N/1) sulphuric acid and the mixture heated in boiling water 
for two minutes. Cool and add 2 or 3 drops of a 10% solution of 
ferric chloride. Then add 5 cc. H 2 S0 4 , Sp. Gr. 1.82. Do not mix. 
In the presence of formaldehyde a blue color will form where the 
acid comes in contact with the lower surface of the milk. 

TEST FOR SODIUM CARBONATE IN MILK OR CREAM 

To ten cc. of the milk or cream add 10 cc. of alcohol and a 
few drops of a 1% solution of rosolic acid. Carbonates are pres- 
ent if a rose red color appears. Pure milk may give a brownish 
yellow color. 

TEST FOR STARCH IN DAIRY PRODUCTS 

Add to a few cc. of the milk or other product in a test tube or 
vial a drop of iodine solution. A blue color shows the presence of 
starch. Dried milk products should be boiled in about 10 times 
their weight of water and cooled before adding the iodine solution. 



DAIEY LABORATORY EXERCISES 155 

TEST FOE BOEATES IN MILK OB CBEAM 

To about 10 cc. of milk in a porcelain dish, add lime water 
until the milk is alkaline. Evaporate the water off and burn to 
an ash. Add two or three drops of hydrochloric acid and a few of 
drops of water. Place a strip of tumeric paper in the solution, 
allowing one end to extend up over the edge of the porcelain dish. 
Again evaporate to dryness at a temperature not above the boil- 
ing point of water. If either borax or boric acid were present in 
the milk, the tumeric paper will change to a cherry-red color. A 
drop of ammonia placed on the cherry-red paper gives an olive- 
green color. 

In testing butter for borax or boric acid, some of the butter 
should be melted and the water and casein allowed to settle. 
Then take 3 or 4 c. c. of the mixture of water and casein that has 
settled at the bottom and proceed with the test as with milk. 

TEST FOB SALICYLIC ACID AND SALICYLATES 

Twenty ec. of the milk are acidulated with sulphuric acid and 
shaken with ether ; the ether solution poured off and evaporated, 
and the residue treated with alcohol and a little iron-chlorid solu- 
tion. A deep violet color will develope in the presence of salicylic 
acid. 

TEST FOB SUCBOSE IN MILK OB CBEAM 

Ten cc. of the sample are mixed with 0.5 gram of powdered 
ammonium molybdate, and 10 cc. of dilute hydrochloric acid (1 
to 10) added. In a second tube 10 cc. of milk of known purity 
are similarly treated. The tubes are then placed in the water 
bath at a temperature of 80°C. An intense blue color developes 
in the presence of sucrose. One-tenth of one per cent of sucrose 
gives a well marked reaction. If the temperature is raised too 
high pure milk may give a color. 

TEST FOB SACCHABATE OF LIME OB SUCBOSE IN MILK OB CBEAM 

To 10 cc. of the milk or cream m a test-tube add 0.5 cc. of 
strong hydrochloric acid and 0.1 gram of resorcinol dissolved in 
5 cc. of water. Shake and place the mixture in boiling water for 
five minutes, when a pink to deep red color gradually develops in 
the presence of saccharate of lime. Pure cream turns yellowish 
or brown. This test does not prove the presence of added lime as 
it is primarialy a test for cane sugar. 



i.16 DAIBY LABOBATOBY EXEBCISES 

TEST FOE GELATIN 

Dissolve one part by weight of mereury in 2 parts by weight 
of concentrated C. P. nitric acid (sp. gr. 1.42) and add 24 times 
its volume of water. Place 10 cc. of this solution in a test tube, 
together with an equal volume of cream. Shake well and add 20 
cc. of water. Shake again, let stand 5 minutes and filter. If 
much gelatin is present the filtered liquid will be cloudy or opales- 
cent. To a little of this liquid in a test tube add an equal amount 
of saturated solution of picric acid. If the solution remains per- 
fectly clear gelatin is absent. Small amounts of gelatin give a 
cloudiness, larger amounts a yellow precipitate upon adding the 
picric acid. 

TESTS FOE AGAR -AGAR IN CREAM 

About 50 grams of cream are diluted with 100 cc. of water 
and the container with contents heated in boiling water and clear- 
ed by the addition of 10% calcium chloride solution. The mix- 
ture is filtered clear preferably in a hot water funnel, cooled, and 
from one-half to two-thirds of its volume of strong alcohol added. 
The precipitate is filtered off and boiled with a small quantity of 
water till no more dissolves, filtered and evaporated down to 5 cc. 
when the solution will gelatinize in the presence of agar-agar. 

Also if gelatin is suspected of being present, before evaporating 
down to 5cc. in the above test, add saturated picric acid solution 
to some of the filtrate when a turbidity or precipitate is produced 
if gelatin is present. In that case the remainder of the filtrate is 
evaporated to 25 cc. and a 10% solution of tannin added, until a 
precipitate ceases to form. To the mixture which must be under 
60° C. are added 5 to 10 cc. of white of egg and the whole heated 
in boiling water for 30 minutes. The solution is> filtered hot and 
concentrated on the water bath to a small bulk, when the pres- 
ence of agar-agar is indicated by gelatinization. 

TEST FOE FLUORIDES 

50 grams of milk or cream are made just alkaline with sodium 
carbonate and rapidly boiled clown in a platinum dish, the fat 
poured off and the residue burned nearly white. The residue is 
moistened with a few drops of Cone, sulphuric acid, and the dish 
covered with a waxed watch-glass having some marks scratched 



DAIEY LABORATORY EXERCISES 157 

through the wax, is heated on a hot plate (80° C.) for half an 
hour, the watch glass being filled with water or ice as necessary. 
After removal of the wax the glass is examined for etching along 
the lines scratched through the wax. 



DAIRY. LABORATORY EXERCISES 



DAISY LABORATORY EXERCISES 159 



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INDEX 

PAGE 
Acid, Adding the 7 

Acid, Effect of Different Strengths 11 

Acid Measure 17 

Acid Reaction of Milk, Reasons for 55 

Acid, Salicylic, Test for 155 

Acid Test 55 

Acid, Sulphuric, Sp. Gr. of 12 

Acidity, Apparent, Real 55 

Acidity of Milk, Importance of 56 

Adam's Milk Fat Method 95 

Adulterations, Calculating for Milk 43 

Agar-Agar, Test for 156 

Albumin 4 

Alkali Tablet Solution, Farrington's 56 

Analysis of Butter, Kohlman Method 99 

Ash of Milk 4 

Babcock, Dr. S. M. 5 

Babcock Glassware, Washing, Specifications for 13-15 

Bath, for Cream Test Bottles, Samples 17 

Board of Health Lactometer 41-42 

Boiled Milk Test 49-154 

Borates 155 

Bulletins, List of 160 

Butter Tat Test, Shaw Method 91 

Buttermilk, Testing 11 

Butter Moisture Test 37 

Butter, Overrun 3 

Butter, Salt in, Salt Test 67, 68 

Butter Yield, Effect of Fat Percentage on 2 

Casein 4 

Cheese, Moisture Test Yield . 3, 62 

Chemicals 17 

Composite Samples, Definition, Care 5, 17 

Condensed Milk, Sweetened, Test for 147 

Cow Testing Association 75 

Cream, Reasons for Weighing for Fat Test 9 

Cream Samples 18 



165 

PAGE. 

Cream Testing,. Directions for 14, 19 

Cream Test Bottles, Specifications for 15 

Cream Test, Tempering and Beading 10 

Dahlberg Method for Casein Solubility 132 

Dividers - 17 

Eixercises, Bart I, Bart II 21, 83 

Error, Limit of in Tests 9 

Evaporated Milk, Tests for 147 

Fat, In Milk Variations and Causes of 3 

Fehling's Copper Solution 147 

Feser's Laetoscope 88 

Fluorides, Tests for 156 

Formaldehyde Test 49 

Formulas for Solids Not Fat 42 

Gelatin, Tests for 156 

Halpen's Test for Cottonseed Oil 136 

Hart's Casein Test 129 

Heeren's Bioscope 88 

Hydrometer 41 

Ice Cream Tests _ 150 

Index 164 

Indicator 56 

Kohlman Butter Fat Method 99 

Lactometer, Board of Health, Quevenne 42 

Laetoscope, Feser's 68 

Machine, Speed of 8 

Measure, Acid 17 

Meniscus 11 

Milk, Composition, Definition 1 

Milk, Specific Gravity of ' 12 

Milk, Mailing Sample ^___ 6 

Milk, Freparing for Testing 6, 17 

Milk, Testing Specifications and Directions 5, 14, 18 

Mjoisture Tests, Butter, Cheese 37, 62 

Majonnier Test - 102 

Mystin, Test for 154 

Normal Solution, Definition of 55 

Overrun 3 

Bhenolphthalein 55 



166 

PAGE 

Proteins 4 

Quevenne Lactometer 42 

Rending Fat Tests 9 

Real Acidity 55 

Reiehart-Meissl Number 139 

Salt in Butter, Test 67 

Samples, Composite Care of 17 

Sediment Test 95 

Shaw Method for Fat in Butter 91 

Sodium Carbonate, Tests for 154 

Solids not Fat, Calculating 4, 42 

Specific Gravity, Sulphuric Acid, Milk, Definition of 12, 13, 41 

Skim-Milk Test Bottle 12 

Specifications, Testing, Glassware 14, 15 

Starch, Test for L 154 

Silicates, Test for 155 

Sucrose, Test for 155 

Saecharate of Lime 155 

Table of Contents V 

Table, Speed of Centrifuge 8 

Tablets, Farrington 's Alkaline 57 

Temperature for Reading Tests 9 

Tempering Tests 10 

Tester 17 

Tests, Defective 19 

Tests, Duplicate 20 

Vitamines 4 

Viseogen 139 

Washing Babcoek Glassware 13 

Walker Casein Test 129 

Water Bath, for Cream Samples, Test Bottles 17 

Weights 17 

Wizard Sediment Test 91 



